82 



SCIENCE. 



[Vol. XIV. No. 339 



this occasion with only a brief reference to infection from the milk 

 and flesh of tuberculous cattle. 



It has been abundantly demonstrated by numerous experiments 

 that the milk from tuberculous cows is capable, when ingested, of 

 -causing tuberculosis. How serious is this danger may be seen 

 ■from the statistics of Bollinger, who found, with cows affected with 

 ■extensive tuberculosis, the milk infectious in eighty per cent of the 

 cases ; in cows with moderate tuberculosis, the milk infectious in 

 sixty-six per cent of the cases ; and in cows with slight tuberculosis, 

 ■the milk infectious in thirty-three per cent of the cases. Dilution 

 ■of the infected milk with other milk or with water diminished, or 

 in sufficient degree removed, the danger of infection. Bollinger 

 estimates that at least five per cent of the cows are tuberculous. 

 From statistics furnished me by Mr. A. W. Clement, V.S., it ap- 

 pears that the number of tuberculous cows in Baltimore which are 

 •slaughtered is not less than three to four per cent. Among some 

 ■breeds of cattle, tuberculosis is known to be much more prevalent 

 than this. 



There is no evidence that the meat of tuberculous cattle con- 

 tains tubercle bacilli in sufficient number to convey infection, unless 

 it be very exceptionally. Nevertheless one will not willingly con- 

 sume meat from an animal known to be tuberculous. This in- 

 stinctive repugnance, as well as the possibility of post-mortem infec- 

 tion of the meat in dressing the animal, seems to be good ground 

 for discarding such meat. The question, however, as to the rejec- 

 ■tion of meat of tuberculous animals, has important economic bear- 

 ings, and has not been entirely settled. As to the rejection of the 

 milk from such animals, however, there can be no difference of 

 •opinion, although this is a point not easily controlled. 



The practical measures to adopt in order to avoid infection from 

 the food, are, for the most part, sufficiently obvious ; still it is not 

 to be expected that every possibility of infection from this source 

 will be avoided. It is difficult to discuss the matters considered in 

 this address without seeming to pose as an alarmist ; but it is the 

 superficial and half knowledge of these subjects which is most 

 'likely to exaggerate the dangers. While one will not, under ordi- 

 nary circumstances, refrain from eating raw fruit or food which 

 ■has not been thoroughly sterilized, or from using unboiled or natu- 

 ral waters in the fear that he may swallow typhoid or cholera bac- 

 teria, still, in a locality infected with cholera or typhoid-fever, he 

 will, if wise, not allow himself the same freedom in these respects. 

 Cow's milk, unless its source can be carefully controlled, should, 

 when used as an habitual article of diet, as with infants, be boiled, 

 or the mixed milk of a number of cows should be selected ; but 

 this latter precaution offers less protection than the former. 



In most places in this country we are sadly lacking in good sani- 

 tary inspection of the food, especially of the animal food, offered 

 for sale. One cannot visit the slaughter-house in Berlin or in 

 Munich (and doubtless similar ones are to be found elsewhere), 

 ■and watch the intelligent and skilled inspection of the slaughtered 

 animals, without being impressed with our deficiency in this re- 

 spect. In large cities an essential condition for the efficient sani- 

 tar5» inspection of animal food is that there should be only a few 

 places, and preferaBly only one place, where animals are permitted 

 to be slaughtered. Skilled veterinarians should be selected for 

 much of the work of inspection. 



It may reasonably be asked that the national government, which 

 has already spent so much money for the extermination of such 

 diseases as pleuro-pneumonia of cattle and hog-cholera, which are 

 not known to endanger the health of mankind, should turn its 

 energies also to means for eradicating tuberculosis from cattle, 

 which is a scourge not only to the economic interests of farmers 

 and dairymen, but also to the health of human beings. 



Without any pretension to having done more in this address 

 than to sketch here and there a few principles derived from bacte- 

 riological researches concerning only some of the most widely dis- 

 tributed external sources of infection, I trust that enough has been 

 said to show the folly of any exclusive dogma as to modes of infec- 

 tion. The ways of infection even in one and the same disease are 

 manifold and various, and can never be resolved into exclusive 

 hypotheses, such as the drinking-water hypothesis, the ground hy- 

 pothesis, etc. 



It follows, therefore, that it is not by sanitary improvements in 

 one direction only that we can control the spread of preventable 

 epidemic diseases. In one situation improvements in the supply 

 of drinking-water check the prevalence of typhoid-fever, in another 

 place similar measures show no such influence ; or, again, in one 

 city the introduction of a good system of sewerage diminishes epi- 

 demic diseases, and in another no similar result follows. We 

 should therefore aim to secure, as far as possible, good sanitary ar- 

 rangements in all directions and in all respects. 



It has also been rendered evident, in what has been said, that 

 infectious agents differ markedly from each other in their behavior ; 

 so that, while public sanitation aims at those measures which are 

 found to be most widely beneficial, it should not forget that each 

 infectious disease is as much a separate problem in its prophylaxis 

 as in its symptomatology, etiology, and treatment. It will not aim 

 to combat cholera with the means found best adapted to scarlet- 

 fever, but it will adapt preventive measures as directly to the spe- 

 cific end in view as possible. In presenting to you the results of 

 researches chiefly bacteriological concerning the scientific basis of 

 preventive medicine, I hope to escape the accusation of one-sided- 

 ness and narrowness by the statement that I do not for a moment 

 intend to imply that the bacteriological method is our only source 

 of accurate knowledge on the subjects which have been considered. 

 My aim is accomplished if I have succeeded in making clear that this 

 method has established facts which aid in a clearer conception of 

 the causes of some important infectious diseases, in a better un- 

 derstanding of the sources and dangers of infection, and in a more 

 efficient selection and application of sanitary measures. 



If this science of only a few years' growth has furnished already 

 acquisitions to knowledge so important, so far reaching, may we 

 not look forward with assurance to the solution of many dark 

 problems in the domain of infectious diseases, — problems the so- 

 lution of which may yield to preventive medicine a future of use- 

 fulness and success which we cannot now foresee ? 



LUCERNE OR ALFALFA. 



During the past two years considerable has been written con- 

 cerning the value of alfalfa as a forage-plant and for hay. Experi- 

 ments in a limited way have been made at the Agricultural Station 

 at Geneva, N.Y., of which Mr. Peter Collier is the director, since 

 1882. 



Alfalfa or lucerne is botanically the same plant {Medicago 

 saliva, Lin.), and one of the clover or leguminous family. Alfalfa 

 has been grown in Greece for nearly three thousand years as a 

 forage-plant. The Romans esteemed it very highly, and Columella 

 writes that it yielded four to six crops a year. In France the plant 

 is known as lucerne, and in Spain as alfalfa. It is grown quite ex- 

 tensively in southern Europe. From Spain alfalfa was introduced 

 into South America, and thence by way of Mexico to California, 

 where it still retains the Spanish name, alfalfa. While in Cali- 

 fornia and many of the Western and Southern States it is grown 

 quite extensively, it has never been much cultivated in the North- 

 ern States. In the Eastern States it was introduced from Europe, 

 and is generally known as lucerne. The alfalfa from California is 

 said to withstand drought far better than the lucerne of Europe, 

 while the lucerne withstands cold winters better than the alfalfa. 



It seems to be the prevalent opinion that lucerne does not flourish 

 well so far north as New York State, but seven years' experience 

 with it at the Geneva station proves that it can and will thrive well 

 in this latitude. Chancellor Livingstone experimented with it with 

 good results on his estate in Columbia County nearly ninety years 

 ago. It has been generally conceded, that, in order to succeed, 

 lucerne must have a deep, sandy, or light loam soil. The experi- 

 ence of the station has been upon heavy clay loam, some of it of a 

 cold retentive nature. This indicates that alfalfa will thrive well 

 upon other than sandy or light loamy soils. Two acres and a half 

 of lucerne now growing at the station, on three parts of the farm, 

 show well the capabilities of the plant to withstand the drought and 

 northern winters. In 1882 two plats were put down to lucerne 

 and alfalfa. These plats have yielded several crops each season 

 since. In 1888 they were cut three times, and yielded an average 



