FIRST CENTURY OF DAIRYING IN NEW SOUTH WALES. 



Among the extraneous causes of abortion none are so mischievous 

 and consequently much to be dreaded as the germs of infection and 

 contagious disease. Of these such as are attended with coughing 

 straining, and restlessness, or which assail the uterus itsel-f, are most 

 to be feared. The influence of the male in the production of abortion 

 appears to have been well established. Many outbreaks of an enzootic 

 character have been well known to arise from the debility and loss 

 of prolific virtues due to excessive usage at the stud. Excessive dis- 

 proportion of the bull as compared with the cow is also said to have 

 the effect of cutting short the term of gestation. 



Is it contagious ? On this point there is a variety of opinion ; and 

 this difference of opinion is quite consistent with the present state of 

 our knowledge, and until the question has been submitted to an ex- 

 haustive experimental inquiry we fear that no definite conclusion can 

 be arrived at. That the disease is capable of being propagated by 

 the cohabitation of pregnant cows with others who have recently 

 aborted there does not appear to be any reason to doubt, and on this 

 fact alone many are satisfied to rest its contagious nature. That a 

 causal connection exists between such animals few will dispute, but 

 there is nothing to show that the extension of the malady under such 

 circumstances is a more necessary consequence of a contagious ele- 

 ment than the sickness we sometimes experience from a disgusting 

 sight or offensive odour is the necessary consequence of an emetic. In 

 both cases the result is quite capable of being explained by reference 

 to impressions operating through the sensorial centres, and exciting 

 what is commonly termed sympathetic action. 



Notwithstanding, however, this explanation of the propagation of 

 abortion, the existence of a specific infection or contagion as a 'factor 

 in the process is by no means rendered impossible, as one fact in the 

 history of this peculiar affection is generally admitted, viz., when one 

 cow in a herd discharges her ovum other cases very frequently follow, 

 and in numerous instances, even to the extent of sooner or later pass- 

 ing through the entire stock. There is nothing in this, however, to 

 establish its contagious nature, for many diseases well known to be 

 destitute of contagious properties will occasionally prevail very ex- 

 tensively among various kinds of animals, where such animals are 

 usually exposed to the same influences. 



In conclusion, if we carefully examine the leading features pertain 

 to the origin, propagation and development of contagious disorders 

 we find : I. That they owe their origin to a morbid element, whose 

 existence can be clearly shown by experimentation. 2. That in order 

 to exercise its specific action it must enter the blood and tissues of 

 the body. 3. That a more or less period elapses period of inoculation 

 between the introduction of the contagion into the body and the 

 manifestation of disease. 4. That when in the blood it reproduces 

 its kind. 5. That during the elimination of the poison, fever is well 

 pronounced. 6. That one attack affords a more or less enduring pro- 

 tection or immunity from -future infection. 



Of abortion it may be said : I. That it is not known to be identified 

 with matter possessing contagious properties. 2. That it has no fixed 

 period of incubation. 3. That except in occasional instances it is un- 

 attended with fever. 4. That one attack predisposes to a second, and 

 is usually followed by several in succession. It may further be stated 

 that in none other of our domesticated animals than the eow is con- 

 tagion ever suspected. 



Chabert, in his veterinary instruction, says : " Abortion sometimes 

 becomes remarkably frequent, and even appears to assume an epizootic 

 or epidemic character in particular districts, or upon particular farms. 

 There are only too -frequently instances of a farmer, who unwittingly 

 introduced an abortion habit among his cows by the purchase of a 



212. 



