was killed eight weeks afterwards, and found to be extensively tuberculous. Part of this animal's lungs and spleen was used to inoculate a five-months-old calf under the skin of the neck. The result showed that the bacilli present had a high degree of virulence for the calf. A tuberculous tumour as large as a child's head gradually formed at the point of inoculation in the neck, and when the calf was killed, eightythree days after inoculation, it was found to be extensively tuberculous in the internal organs, tubercles being present in the lungs, liver, spleen, and kidneys, as well as on the pleura and peritoneum and in several groups of lymphatic glands.

In the other experiment recorded by Professor Wolff, he attempted to infect a calf by subcutaneous inoculation with mixed sputum from five consumptive human beings. In this case therefore there was every reason to suppose that the bacilli employed were human and not bovine. The result showed that the bacilli were much less virulent than in the previous case, for when the calf was killed, ninety-three days after inoculation, the disease was found to have spread from the point of inoculation to the adjacent lymphatic glands, but it had not extended to the internal organs. The experiment, however, according to the author's interpretation of it, proves that, contrary to Koch's general assertion, human tuberculosis can be transmitted to cattle.

It may be well to add that in all the before-described experiments the calves and other bovine animals employed had been previously tested with tuberculin, and had not reacted.

It thus appears that quite a number of entirely independent observers have experimentally proved that the tubercle bacilli found in the lesions of human beings are sometimes virulent for cattle. It is impossible to reconcile these results with the declarations made by Professor Koch at the British Congress on Tuberculosis. If the statement that human tuberculosis cannot be transmitted to cattle is true, then in all the cases, already considerable in number, in which cattle have been infected with bacilli taken from human lesions, the disease from which the human patients suffered was not properly speaking human tuberculosis, but bovine tuberculosis contracted from cattle. In other words, it would have to be admitted that the bovine disease is transmissible to human beings, and that in natural circumstances it is in a good many cases actually transmitted. On the other hand, if Koch was in error in supposing that tubercle bacilli which have for a number of generations been passed on from human patient to human patient (human bacilli properly so called) are always inoffensive for cattle, it is possible that none of the human

Present Position of the Controversy.

393

cases referred to in the preceding pages had anything to do with bovine tuberculosis, but were merely cases in which the bacilli possessed a degree of virulence much above the average. Obviously this admission would very seriously weaken the practical importance of Koch's contention that human and bovine tuberculosis are distinct diseases, for if the human bacilli are sometimes virulent for cattle, it is reasonable to suppose that bovine bacilli may sometimes be sufficiently virulent to infect a human being.

1

In searching for evidence as to the present position of the controversy regarding human and bovine tuberculosis, one may turn in the next place to the proceedings of the International Conference on Tuberculosis which was held in Berlin in October last, and which devoted a special meeting to the discussion of the transmissibility of bovine tuberculosis to man. The discussion was opened by Dr. Koehler, President of the German Imperial Health Office, who impartially reviewed the evidence for and against the view that human and bovine tuberculosis are identical diseases, and in concluding summarised his own estimate of the position by saying that neither the identity of the human and the bovine disease, nor the transmissibility of the bovine disease to man, had yet been proved one way or the other. He pointed out that in Germany tuberculous meat and milk had never been regarded as the most important cause of tuberculosis in human beings, and hinted that the laws now in existence with respect to the sale of tuberculous products from animals would probably have to stand, even if it were demonstrated that the human and the bovine diseases were distinct. Apart altogether from the alleged danger of infection attaching to tuberculous meat, the emaciated carcasses of tuberculous animals and the parts actually diseased would always have to be condemned on account of their repulsive appearance.

Most of the subsequent speakers openly espoused the one or the other view of the question, some maintaining that the transmissibility of the bovine disease to man could no longer be contested, and others holding that the bulk of the evidence supported the position taken up by Professor Koch at the Congress in London. Professor Koch himself brought the debate to a close. In a speech of great length he submitted to a searching criticism the cases which had been cited as actual examples of the infection of human beings with tuberculous meat or milk, and with great force contended that not one of them was absolutely convincing. He urged the members of the Conference to discard as untrustworthy all the cases that

'Deutsche Med. Wochenschrift: 1902, Nos. 45 and 48.

had hitherto been brought forward, and to set themselves to collect reliable information bearing on the infection of human beings with either meat or milk. It is very important to notice the conditions which in his view require to be fulfilled in any case in which it is sought to prove that the bovine disease has actually been transmitted to man. They are as follows :—

1. It must be proved by a clinical history that is not open to any doubt, or by post-mortem examination, that the disease from which the patient suffered was tuberculosis.

2. Every other source of infection than meat or milk must have been certainly excluded. The mere fact that the patient came of a healthy family will not suffice, for every person is exposed to many other risks of infection, both in his own family and outside.

3. In every case of alleged infection through milk the history of all those who partook of the milk must be taken into consideration. When these have been numerous, and only one of them has become ill from tuberculosis, it must be regarded as highly improbable that that one person owed his infection to the milk.

4. It must be proved that the incriminated milk came from a tuberculous udder, and not merely from a cow affected with tuberculosis.

Only two remarks need be made regarding these remarkable postulates. One is that if every person is exposed to other risks of infection than those attaching to meat and milk (which is highly probable), the second condition cannot possibly be fulfilled in any case. The second remark is that if every person is exposed to the risk of contracting tuberculosis, apart from the consumption of tuberculous meat or milk, and if only a small proportion of the population become visibly tuberculous, it does not appear to be justifiable to impose the third condition. If the great majority of people escape the risks to which all are exposed, why should no case of alleged infection through milk be admitted unless the majority of those who consume the milk become visibly ill?

Only one other sentence from Professor Koch's speech need be quoted, viz., the following:-" At the same time I cannot and do not wish to deny that occasional cases [of infection through milk] may occur." This does not indicate any change in Professor Koch's attitude since he attended the Congress in London, for, contrary to the general impression in this country, he did not on that occasion maintain that bovine tuberculosis is never transmitted to man. He merely expressed the opinion that the danger in this connection was so slight that it was not necessary to take any precautions against it.

Koch and Transmission of the Bovine Disease to Man. 395

At the Berlin Conference, mentioned above, Dr. G. A. Heron' read an address on the present position of the conflict with tuberclosis in England, and in referring to bovine tuberculosis, he informed the Conference that the law prohibited the sale of tuberculous milk and meat; but that since Professor Koch's famous statement at the London Congress in 1901 the enforcement of the law seemed to have become relaxed, without any marked influence, however, on the death-rate from tuberculosis.

It need hardly be said that in this country there is no law which expressly forbids the sale of tuberculous meat, and that the omission is of little consequence since only a small part of the meat consumed in this country is submitted to inspection. With regard to the sale of tuberculous milk, it is notorious that there is no general law which imposes any serious check on the sale of such milk, and there does not appear to be any justification for the assertion that public health authorities have been less energetic in their endeavours to secure a pure milk supply since July, 1901, than they were before that date. It is a little unfortunate that the Berlin Conference should have been misinformed with respect to these points. ED.

WOOL PRICES IN GREAT BRITAIN.

WOOL, in common with other agricultural produce, has undergone in recent years a considerable depreciation in price. The important position at one time occupied by this commodity suggests that the following account of the fluctuations in the value of the leading varieties of wool, based on an article which I contributed to the current Volume of the Royal Statistical Society's Journal,' may be of interest to the British farmer. In attempting to deal, however inadequately, with these variations in price, it is impossible to avoid statistical

1 The Lancet, November 1, 1902.

2 Journal of Royal Statistical Society, Vol. LXV., September, 1902.

methods, which perhaps lend a somewhat formidable appearance to the subject; but the facts are nevertheless of sufficient practical interest to repay the trouble of examining the Tables in which they are embodied. The comparisons thus made also afford an opportunity of indicating the extent to which British varieties have suffered as compared with those grades which now constitute the bulk of the wool consumed in this country.

As the price of each kind of wool depends primarily on certain natural characteristics, which differentiate it from other kinds, the most exact method of measuring the changes will be perhaps to express the annual average price as a ratio or percentage of the value in certain selected years. The mean of the average prices in the three years 1883-85 has therefore been chosen as a convenient starting point and basis of comparison. At that period wool and commodities generally had fallen very considerably from the level of the sixties, and seem to have reached a point with which subsequent years may fairly be compared. The variations from this standard can easily be seen, and the relative depreciation of each class accurately measured.

The descriptions of wool on the market, each with its own peculiar characteristics, are very numerous, but I have endeavoured to make a selection which should be typical of the two great classes, viz., merino and cross-bred, and have also included the principal home-grown kinds. The price of merino wool is illustrated by four varieties, viz., Port Philip, average fleece; Port Philip grease, good average; Adelaide, average grease; and Cape Eastern. Buenos Aires wool is

another variety of merino to which prominence might be given, but it has not been much imported into this country, most of it going to the Continent. For cross-bred, two sorts of Australian, medium and coarse, have been taken, and with these English half-bred and Down wools are contrasted. Lustre wool is represented by Lincoln and Leicester; and, in addition, the produce of the Cheviot and Black-faced breeds of sheep, though not of great commercial importance, is included, as being of considerable interest in this country.

The first place must be given to merino, the finest stapled and most valuable class of wool, and also that which is most widely produced. It comprises the production of a large proportion of the flocks of Australasia, the Cape, and the River Plate; and in the early years of the period under review it was almost the only sort of wool imported into the United Kingdom from those countries. Table I. shows the average annual prices, quoted by the Yorkshire Daily Observer, of the varieties named above.