RECENT PROGRESS OF ORGANIC CHEMISTRY.

587

any other liquid, charged with carbonic acid, cannot give out that gas in an atmosphere of carbonic acid, nor in one where that gas is present in large proportion, neither can it take up the oxygen necessary to convert it into arterial blood. All this it can do in an artificial atmosphere containing much carbonic acid, if oxygen enough be present to allow of the diffusion. In hydrogen gas, the venous blood diffuses out its carbonic acid, and is, pro tanto, arterialised, but life can only be sustained for a very short time, by means of the residue of oxygen remaining in the blood. Death occurs here from want of oxygen, but not because the carbonic acid is retained, as in an atmosphere of carbonic acid, where death is instantaneous. The researches of Regnault and Reiset have also cleared up many other points in respiration, which I must here pass over.

Liebig has shown, that the absorption of carbonic acid by the blood is a chemical, not a mechanical process, depending in great part on the presence of alkaline phosphate (or phosphate and carbonate) of soda. Solutions of these salts, so different in all other respects, agree in absorbing carbonic acid in proportion to the amount of salt, 1 per cent. causing water to absorb twice as much as pure water, while blood absorbs about ten times as much as pure water. The absorption of oxygen in the lungs is partly mechanical, since a solution charged with carbonic acid, in contact with air, or agitated with it, gives out its carbonic acid, and takes up, in its stead, a certain amount of oxygen; and partly chemical, the chemical action probably depending on the presence of a compound of iron, analogous to the protoxide. The poisonous action of hydrocyanic acid and of sulphuretted hydrogen probably depends on their decomposing this compound of iron instantaneously, and rendering it unfit for use.

In regard to nutrition, Liebig has also, in the forthcoming new and much enlarged edition of his "Letters on Chemistry," made various important remarks. The fact that animals die, with the symptoms of starvation, when fed exclusively on fibrine, on white of eggs, or on caseine, as well as when fed on sugar or starch, depends on the absence of the necessary salts, which, in flesh, are found partly in the fibrine, partly in the juice; in eggs, partly in the white, partly in the yolk; and in milk, partly in the caseine, partly in the whey. When the juice, yolk, and whey respectively, are removed, life can no longer be sustained, as on the original food. Further, the presence or the formation of oil or fat appears to be essential to the formation of cells, although the greater part of the fat is burned off or oxidised. It would appear that the liver produces some substance, possibly a ferment, which has a share in the production of fat in the body; but this requires investigation. As fat enters into the composition of nervous matter, this is a point of much interest, as we know not yet where the nervous matter is formed.

Again, the blood cannot exist, nor retain its fluidity, except as an alkaline fluid; and yet it would appear that tissues can only be formed in an acid fluid, where free phosphoric acid or acid phosphates exist. Such is the case with the juice of flesh. The yolk of egg contains, beside albumen, oil and free phosphoric acid, as well as salts. Hence the chick is developed from the egg alone. If we examine the proportions of sanguigenous matter, and of non-nitrogenous elements of respiration in food, the latter being calculated as starch, we find the following general results :—

Milk of the cow,
Human milk,
Leguminosa (seeds),
Grain,

Sanguigenous.

Starch.

20 to 30 50 to 60 27 to 30

ETE

Fat mutton or pork,

Beef,

Hare,

Veal,

Potatoes, white and blue,
Rice and Buckwheat,

86 to 115

123 to 130

Here we see that milk and grain contain starch and sanguigenous matter in the proportion of from 30 to 60 of the former to 10 of the latter. Within these limits are the best proportions; 30 or 40 to 10 for growing, 50 or 60 for adult animals. It is obvious that beef, especially if lean, contains too little starch (fat calculated as starch); and that potatoes and rice contain too much. The indigestibility of veal by itself is accounted for. It is an approach to pure fibrine, and is also deficient in salt and iron. But the instinct of man has taught him to use a mixed diet, such as yields the proportions found in milk or in grain. Thus, he mixes fat bacon with beans; pork with pease-pudding; beef with po tatoes and cabbage; mutton with rice; veal with ham, without any knowledge of the principle. Nay, if confined exclusively to lean flesh as solid food, he would find wine, beer, or spirit necessary to give the proper balance; for alcohol can replace fat or starch as an element of respiration. Added to lean flesh, it yields a food like milk; to fat flesh, a food like rice or potatoes. Of course, with a mixed diet, it is superfluous, if not injurious.

On the other hand, while a due proportion of the two chief elements of food is essential to nutrition as well as to respiration, it is to be observed, that the compounds of nitrogen, including the sanguigenous bodies, are exceedingly difficult of combustion or oxidation, combination with nitrogen depriving even phosphorus and nitrogen of their combustibility. Hence they are never oxidised in the body, so long as fat, starch, or sugar is present; and one function of the latter bodies is, to protect the tissues against the action of oxygen, which, in starvation, ultimately consumes them. In reference to the amount of heat given out, the chief elements of food stand as follows::

100 parts of fat produce as much heat, when oxidised, as

240 of starch,

249 of cane-sugar,

263 of grape-sugar,

266 of brandy containing 50 per cent. of alcohol,

770 of lean flesh.

Again, while we know that the food may vary greatly, within certain limits, without affecting the vital processes, the excreta vary with every change of diet. We have, therefore, the valuable power of changing, for example, the nature of the urine by a diet founded on a knowledge of the composition of food. I would again refer to the forthcoming edition of Liebig's "Letters on Chemistry" for a succinct view of what has lately been done in this and in many other parts of the subject. I had hoped to have been able to lay before you an account of Liebig's own latest researches in Animal Chemistry, as well as of those of many other chemists, all of which will appear in the "Letters." But unfortunately, the last ten sheets, which, as well as an equal quantity of what is already thrown off of the new edition, are entirely new, have not yet reached me, so that my sketch of this part of the subject is necessarily imperfect. This is the less to be regretted, as your time would have compelled me to be very brief, so as not to do justice to the subject.

Finally, I think it will appear, even from this very imperfect sketch, that, without a knowledge of chemistry, real progress in true physiology and pathology is hopeless. These sciences have been deeply indebted to anatomy, and the increasing applications of the microscope are daily doing wonders. But to Anatomy, Chemistry must be added, because the changes we have to study, apart from structure, are chemical; and the next generation of great physiologists and pathologists will be men who shall combine the two methods of research. We may well envy our pupils and successors the rich harvest of valuable discoveries which certainly awaits them; for there never yet has been a time when the successful co-operation of all the sciences relating to physiology was so probable as now, or promised such vast results.

Part Fourth.

PERISCOPE.

MEDICINE.

MODE OF PROPAGATION OF MEASLES. BY DR PANUM OF COPENHAGEN The Faroe Islands, situated, as is well known, between Shetland and Iceland, were in 1846 invaded by an epidemic of measles. The disease, which had commenced in April, ceased in October, and of 7782 inhabitants, more than 6000 suffered from it. Since 1781, it may be literally said, that not a single case of measles had been observed among them-hence all were ready to receive the contagion. Still there existed certain remarkable and exceptional conditions, which may assist in explaining the enormous extension of the epidemic. Not only are the Færöe Islands separated from the rest of the world by their geographical position; but, by a commercial monopoly which has existed for ages, the islanders have no right to sell the produce of their industry except at the government counting-house (comptoir), and here only can they procure articles for their own consumption. Such extreme isolation ensures an almost complete immunity from contagious diseases. The mean duration of life is in these islands very high, and the most considerable mortality occurs between 80 and 90.1 The climate and mode of life are far from favourable; hence it is to the absence of epidemic and contagious influences that the low rate of mortality is attributable. Unfortunately no sooner does a contagious disorder find its way into the islands, than the extreme misery of the inhabitants causes it to assume a degree of intensity for which a parallel can scarcely be elsewhere found. While in Denmark measles is chiefly seen among infants, and for the most part spares adults, I have seen villages among the Faroe Islands, where of 100 peasants more than 80 were at the same time confined to bed. The Danish government was obliged to send out two physicians, Dr Manicus and myself. The circumstances above mentioned the peculiar position of my field of observation-have enabled me to gather some information on the subject of the contagious property of measles, which may perhaps be read with interest.

There are seventeen inhabited islands, separated by straits, which the currents render it dangerous to cross. The mountainous nature of the soil compels the inhabitants to cluster together along the coasts. There have thus arisen villages, of which the most populous hardly number more than 200 inhabitants -the town of Thorshavn, the seat of government, contains only 800 souls. Each village forms a sort of family without communication with the neighbouring localities. To such a degree is isolation pushed, that the presence of a stranger, or of an inhabitant from a neighbouring village, is immediately known to the whole community, is often even set down in the calendar as a marvel, and long continues a subject of conversation. Fears excited by the epidemic of measles rendered intercommunication even more guarded. I could almost, in each village, follow the disease from its first appearance, tracing its progress from individual to individual. The reader will consequently understand what unusual facilities I possessed for studying the mode of propagation of measles, during four months spent on thirteen out of the seventeen islands.

The length of the period of incubation of measles is far from satisfactorily

"La plus grande mortalité tombe entre 80 et 90 ans." We quote the author's words, as the fact recorded sounds rather startling.-ED.

determined-different authors state it at eight, ten, and fourteen days. Others, with more reserve, assign no fixed and regular period to the first stage of the disease. In great cities it is impossible to ascertain at what precise moment an individual has been subjected to the contagious influence. To obtain results of sufficient accuracy, the observer must be placed in similar circumstances to myself on the Færöe Islands.

The first native attacked with measles was a labourer, now resident at Thorshavn. He had left Copenhagen on the 20th March, had arrived on the 28th in perfect health, and became ill on the 1st of April. About fourteen days afterwards his two most intimate friends showed the first symptoms of the disease. This case, which I did not personally witness, excited my attention and induced me to undertake a series of observations on the duration of the incubation.

On the 4th June, ten men of Tjornevig, sailing in the same boat, had taken part in a great fishing expedition with the inhabitants of another village. On the 18th June all ten were affected with measles, after two to four days of premonitory symptoms. They had been in contact only with the fishers from Westmannhavn, who were either convalescents from the same disease, or had been living in the midst of others affected by it. In from twelve to sixteen days after the appearance of the exanthema in these ten individuals, almost the whole population of the village were covered with the same eruption.

Here, then, was sufficient reason for suspecting that the contagion might lurk in the organism in a latent condition, or at least without exciting the specific eruption, for a period of from thirteen to fourteen days. In fifty-two localities I collected accurately the names of persons first affected with measles, the date of the appearance of the eruption, and the date of the invasion of the disease in the inhabitants to whom it spread. It would be worse than useless to introduce each of these tables here; it is enough to say that everywhere facts confirmed my original supposition, and that no exception to the rule occurred. I shall merely mention, in a summary manner, some observations which establish, in the most conclusive way, the numerical results obtained.

At Hattervig, a young man, the first sufferer, assured me that the eruption in his case appeared ten days after his arrival in an infected village. This was a solitary instance, and the patient afterwards contradicted the false information which he had given me. At Fuglefjord, the daughter of my host was cured of the disease from which the other nine members of the family had not as yet suffered. I asked on what day the rash had appeared on the girl, and taking an almanac, made a stroke under the fourteenth day, telling the family that this was the date when the disease was likely to appear among them. I learnt, on my return, that this prediction had been but too accurately verified by the eruption appearing on all the nine.

The Great Dimon is a very little islet, inhabited only by a family of eighteen persons. A boat, manned by some of the men, visited Tveraa, where the epidemic raged, and where the boat remained only a few hours. Ten days afterwards the whole boat's crew were in their ordinary health-on the fourteenth day all had the eruption of measles, and fourteen days afterwards the rash, with the same regularity, appeared on all the remaining members of the family.

At Skaalevig, the only one of the islands where the houses are isolated, standing at considerable distances apart, the contagion spread less rapidly, but in following its successive outbreaks even here, the law which I have laid down was found to be equally observed.

Hence I believe it may be regarded as a constant law, that the contagion of measles, once introduced into the system, does not at first manifest its presence by any sign, and that after a premonitory stage of indeterminate duration, the eruption makes its appearance on the thirteenth or fourteenth day after infection. Undoubtedly peculiarities in the constitution, regimen, &c., of individuals, may hasten or retard the appearance of the exanthema, but these influences are far less potent than, a priori, might be supposed. The greatest variation on one side or other of the period specified, is at the utmost twenty-four hours. After

寳

S

MEDICINE.

the striking coincidence of the observations which I have made in fifty-two villages, ought not exceptions (which I have never met with), if they exist, to be 591 accounted for by the inexactitude of the observer? Whenever I have been inelined to contest evidence, which at first seemed to shake my conviction, I have finally found, that far from invalidating, it served to confirm the rule laid down. According to observations made at Copenhagen, the incubation of variola extends through fourteen days. The analogy between these two eruptive diseases, seems to me to attach considerable interest to these observations.

A circumstance which causes some uncertainty in prosecuting such researches is the indeterminate duration of the premonitory catarrh. suffered six or eight days before the eruption from cough, slight ophthalmia, and febrile disturbance; in others, these symptoms were not noticed till four or six Some of my patients days before the rash; in the majority they were not observed till within a period of from two to four days immediately preceding the exanthema. Exact numerical results can only be obtained by comparing the date of contact with the sick and that of the appearance of the measles.

If we admit as a principle, that the incubation occupies from thirteen to fourteen days, and if, on the other hand, instances, both numerous and well authenticated, prove that there generally elapse exactly thirteen or fourteen days between the first symptoms of eruption on an individual, and its subsequent appearance on others, to whom he communicates it, is it not evident that the contagion is effected during the eruptive stage? We may at least conclude that measles in the latent stage is not contagious. Is it so during the premonitory stage? It is difficult to decide. Although I am acquainted with no facts which demonstrate the possibility of transmission during the simply catarrhal stage, I am not prepared to establish the contrary.

It is generally believed that measles is peculiarly contagious during the desquamative stage. On what foundation does this opinion rest? I cannot tell : for my own part I have never seen a case to convince me that contagion took place at the desquamative period. The transmission, if the period above assigned to the incubation be regarded as constant, is almost always, if not in every case, effected at the period when the spots make their appearance. Never, in the course of the events which I witnessed, was an individual attacked with measles more than fourteen days after the disappearance of the exanthema from the individual who might have infected him. gious at the outset, and during the course of the eruptive stage; it is, on the other hand, doubtful if it be contagious at all in the catarrhal or desquamative stages. In a word, measles is highly contaAs for the second attacks of measles, it is remarkable that all the old people of the Færöe Islands, who had suffered in the epidemic of 1781 (and of these there were many), escaped in 1846; I could cite a hundred instances from my own observation. This fact is the more conclusive, since age (even very advanced) in no measure diminishes the susceptibility. As far as I know, very old persons, who had not been exposed to the earlier epidemic, all suffered from the recent one, while certain young people living in the midst of the disease were spared. The degree of intensity with which we may suppose the contagious principle of rubeola endowed, is not well defined. The following facts will, perhaps, throw a little light on this subject. On the 2d June a crew embarked at Klaksvig, to fetch articles of merchandise from Funding. They were prevented from returning till they had helped to unlade a vessel on board of which were men just recovering from measles, which also prevailed extensively in the port. They entered no house in Funding but the counting-house. On returning, the men of Klaksvig threw away the coverings of their merchandise, washed themselves carefully, changed their clothes, &c. None of them caught the disease till the 3d July, when it first made its appearance in Klaksvig. But five inhabitants of Nordre-Gjov, who had accompanied them to Funding, and on their return had not used the same precautions, although exposed to the same influences, suffered on the fourteenth day after their exposure to the contagion.

When I arrived at Klaksvig, such was the terror of the islanders, that nobody