specially affects the air passages! What applies to speaking applies to a still greater degree to the act of coughing or sneezing.

To Schäffer we owe the discovery that leprosy bacilli may be disseminated in immense numbers by the coughing of leprosy patients, whilst it has been estimated that a tuberculous invalid may discharge a billion tubercle bacilli in the space of twenty-four hours, whilst the dried sputum of consumptive persons has actually engendered tuberculous symptoms in the lungs of animals which were made to inhale it. Plague bacilli have been found in masses in the mouths of plague patients, and were found, moreover, before any symptoms of the disease had declared themselves; and the sputum of infected persons is regarded by some authorities as one of the most important vehicles by which plague is spread. The culpability of air in the dissemination of tuberculosis amongst animals has been made the subject of some very exhaustive and valuable investigations by Kasselmann. In as many as 71 per cent. of bovine tuberculosis cases the respiratory organs, Kasselmann found, were the seat of the disease. The undoubted contamination of the air which takes place in the surroundings of tuberculous animals is not, however, due to the bacilli being exhaled by such cattle in the mere process of

respiration, for it has been repeatedly found by various investigators that the air expired by infected animals is free from the dreaded tubercle bacteria. As in man, so in animals-it is by the act of coughing that tuberculous secretions are discharged through the mouth and nasal passages, some of which in the form of spray may enable the bacilli to remain suspended in the air for periods of five hours or more, whilst other portions of such secretions fall on the ground or in the feeding troughs, and later on, as dust, may again relentlessly claim their toll of victims.

In other cases of tuberculosis the excrementitious matter becomes, of course, a fertile source of infection to the surroundings. The dire results which may follow the introduction of a single tuberculous animal into a healthy stall of cows may be realised from the fact that in one instance a whole herd of twenty-eight animals became in the course of one year infected in consequence of the admission of one diseased cow, the cow-house having previously had a perfectly clean bill of health in this respect.

On the Continent the risk of wholesale infection by such means is greater than in this country; for abroad the animals are to a much greater extent stall-fed, and kept shut up both winter and summer. A case is mentioned by the well-known veterinary authority, M. Nocard, of a whole stall

of animals becoming infected through the cowman who tended them being consumptive. He slept in a loft over the cows, and his tuberculous sputum in the form of dust was conveyed to the stalls beneath and so spread the infection.

It has been stated on high authority that domestic pets such as parrots may contract consumption from their masters, and that no less than thirty-six per cent. of these birds brought to the veterinary college in Berlin are found to be suffering from tuberculosis.

In that much - dreaded South African cattle disease, rinderpest, the infection, contrary to what is found in the case of tuberculous animals, is principally spread by the materies morbi being liberated in the air expired by afflicted cattle, the contagious area surrounding an infected animal extending to as much as a hundred yards and more. Again, as regards pleuro-pneumonia in cattle, the contagion is given off in the air expired, and owing to the length of time which elapses before the lung becomes completely healed and healthy, even after a period of from six to nine months, the expired air may still prove a source of infection.

In an official report on the open-air treatment of consumption in Germany a case is mentioned in which the patient, a farmer by occupation, had

contracted the disease from some tuberculous cattle which he had on his farm. The writer goes on to say, "This case is worthy of special attention, inasmuch as it indicates that in addition to the danger of contracting the disease from the use of milk or meat derived from tuberculous animals, the tending of such animals may serve to convey the infection to man possibly much more frequently than has hitherto been supposed."

In addition to the above instances of the responsible part played by air in the dissemination of consumption many others might be cited, but perhaps the most striking is that in which a scientific assistant of Tappeiner contracted the disease, and succumbed to it, in the course of some experiments which were being made to ascertain whether consumption could be communicated to animals by spraying them with an emulsion of the sputum of consumptive patients.

It is of historical interest to note that these experiments were being conducted by Tappeiner three years before Robert Koch made the now classical announcement to the scientific world that he had succeeded in identifying, isolating, and in cultivating outside the human body the specific cause of consumption in the shape of the now familiar bacillus tuberculosis. The opinion expressed by Koch at the Congress on Tuberculosis

recently held in London, that human and bovine tuberculosis are distinct diseases, is still the subject of contention and experimental investigation. Even if the opinion of this great authority is correct, and in this connection it is interesting to note that already in 1896 this opinion was brought forward by Smith in the Medical Record at a time when Koch was maintaining the identity of human and bovine tuberculosis-granted that Koch is correct, it should not, as so many fear, cause any relaxation in the efforts which have been at last made to safeguard our dairy produce by reasonable hygienic precautions; for even if tuberculosis is not transmissible from the cow to man, we know that in the hygienic supervision of our dairy industry we place a great barrier between us and the bacillus tuberculosis and those numerous other disease germs which can and do gain access to milk from the personnel of a dairy and so spread infection. With the alarming prevalence of consumption is it not justifiable to regard as certain that a definite proportion of the people engaged in milking, for example, are consumptive? And knowing, as we now do, how such persons can give off the germs of the disease in the simple act of speaking, the contamination of our milk with human tubercle bacilli must be regarded almost as a certainty. Would it not be reasonable that a code of simple