On Abortion in Cows, 



this is not invariably the case, we are at the same time bound to 

 confess that unless abortion be clearly dependent upon some 

 temporary and accidental cause, it very frequently befalls a 

 number of cows in the same stock the same season. In this, 

 however, there is nothing to establish its contagious character^ for 

 many diseases well known to be destitute of contagious pro- 

 perties will occasionally prevail very extensively among various 

 kinds of animals. Much more than the simple extensive pre- 

 valence of a disease is required to prove its contagious nature : 

 we must show, 



a. That animals subjected to its supposed influence are affected 

 in greater numbers than others ; thus, on introducing an animal 

 or animals affected with a disease among healthy ones, the latter 

 to a greater or less extent within a certain time are affected by 

 the same disease. 



h. That the separation of diseased from non-diseased animals 

 has a perceptible effect in arresting extension of the malad^^ 



c. That those animals earliest and most closely connected with 

 the sick are first affected. 



d. That large numbers of animals remain unaffected so long 

 as they do not mix with those which are diseased, although they 

 live in the same building or neighbourhood inhabited by those 

 among whom the disease existed. 



Now, admitting that abortion in its ordinary occurrence is a 

 disease, and although, as has been stated, it may be induced by 

 causes of various kinds (some of which have been named), yet, 

 having once occurred among a stock of cows, its further exten- 

 sion among them does at first view seem conformable to the con- 

 ditions here laid down as proving the character of diseases to be 

 contagious. For cases can be adduced to show that when one 

 or two cows in a herd have, from whatever cause, cast their calves, 

 others pregnant will do the same ; and that on a careful and early 

 separation of those first aborting from others still pregnant, the 

 latter remain unaffected. 



There are, however, other considerations to be entertained 

 here. In contagion we assume that matter in some tangible 

 form, or minutely and invisibly diffused in a gaseous condition, 

 emanating from a diseased animal, passes to some absorbing 

 surface in the body of a healthy one, and there becoming further 

 developed, produces disease also. We think the strongest advo- 

 cate of contagion in the present instance is not prepared to assert 

 that the discharge incident to abortion can be transmitted from 

 the body of one cow to another in the ordinary course of things ; 

 and even if such transmission could be effected, we can hardly 

 imagine how abortion could be induced thereby. It is, however, 

 said that the odour attendant upon these discharges^ on being 



