322 STATE BOARD OF AGRICULTURE. 



iuipoitation of cattle from countries south of tliein. Sweden follows closely upon 

 Denmark in the amount of tuberculosis, and into Norway, where tuberculosis ia less 

 rife, there is less importation. Enj^land has been in close communication with the 

 continent and has produced a good development of the disease. It is fair to suppose 

 that all the newer countries, as America, ^Vu.stralia, New Zealand, have U'cei\ed their 

 share through importation from the older countries. That one diseased animal ij cap- 

 able of conveying the disease to a herd of sound animals has been repeatedly demon- 

 strated. Sections which have been practically free from imported stock are at the 

 present time practically free from tuberculosis. Dr. Pearson of Pennsylvania gives an 

 illustration where such a condition has existed. The common practice of placing 

 pure bred stock which are directly descendent from imported stock, or have beeij 

 recently imported, with the native herd, in order to build up the herd, is a pernicious 

 practice in some ways ; for one or two animals thus introduced may be the means of 

 eventually destroying the value of the wliole herd. I believe tliat stock growers and 

 dairymen are beginning to realize tliat thi.s is the greatest possible chance of ruining 

 their herds through tuberculosis. 



SUSCEPTIBILITY TO TUBEKCULOSIS. 



There is no phase of this subject which is so enshrouded in ignorance as individual 

 susceptibility to this disease. Although the presence of the germs are essential for 

 its development, yet there must be besides the germs a specific diathesis. The tubercle 

 bacilli may be present in the body tissues and yet be unable to produce the disease, 

 therefore there must be a concomitant relation existing between the tubercle bacilli 

 and tissues where they find their lodgment before tuberculosis can be established. To 

 account for the preparation of the tissues to receive the bacillus several factors are 

 induced, no one of which may be said to be the most important. 



Improper ventilation has been frequently associated with bovine tuberculosis. For 

 this reason it is claimed that this agent plays a part in the production of the disease. 

 It is readily understood, although inexplicable, that a failure in supplying the neces- 

 sary amount of fresh air would lead eventually to a lessened vigor of the body tissues. 

 In another way facts seem to establish a definite bearing of ventilation vipon tuberculo- 

 sis. Where the tuberculin test has yielded the greatest number of victims, there has 

 been in the majority of cases a close, poorly ventilated and perhaps badly lighted stable, 

 in which sufficient air for a free exchange would be impracticable. An efTort to secure 

 warmth, througli kindness and economy, seems to have led to unsatisfactory results. 

 Yet it is claimed that tuberculosis is little prevalent among the Esquimaux. If this 

 statement is true, the huddled condition of this people in their small huts would 

 hardly coincide with the foregoing views. Notwithstanding this, it would seem 

 probable that if the habits of the Esquimaux were transferred to Michigan there would 

 be little opportunity of anybody's indulging in them to escape the white plague. The 

 American Indian appears to have been free from tuberculosis until the advent of the 

 white man. With the corralling of the Indians upon reservations and with the intro- 

 duction of many of the customs of the white man, tuberculosis has developed to such a 

 degree that it is a veritable plague which threatens the eradication of the whole race. 

 Living under original and natural conditions, largely in the free, open air, they were 

 able to ward off or evade the disease which now so sadly afflicts them. Although in 

 following up the evidence in this matter both sides oflTer substantial illustrations, still 

 we cannot help concluding that improper ventilation does exert some influence in 

 preparing the tissues for the reception of the germ. 



There is nothing so baneful in the Aveakening of constitutional vigor as in-breeding. 

 Of course we do not claim that this is in any way the direct cause of tuberculosis, 

 yet we believe that it paves the way for infection. In-breeding in man is not permis- 

 sible, but as we pass down in the grade of animals, it becomes less and less noticeable, 

 until in the case of the lowest animals, in-breeding may be carried out witli impunity. 

 In the bovine species it is verj' doubtful whether in-breeding may be allowed with much 

 greater advantage than in the human species. Great attention is given at the present 

 time in breeding to type. If this is possible, does it not seem just as plausible to 

 breed into the offspring exaggerated weaknesses through in-breeding processes? It is 

 not necessary that this weakness be as visible as the udder on a cow, for it may be 

 resident in the tissues and permeate the whole body. Supposing the father is robust 

 and the mother possesses a weakness of the stomach (in human parents) the offspring 

 is likely to inherit that weakness from the mother. Supposing now that this weakness 

 be a family disorder and then the mother and the father came from one branch or other 

 of the family, what would be the natural result? The weakness must be exaggerated. 



