600 PLEUEO -PNEUMONIA. 



Fourthly, The animals, whether slightly or severely af- 

 fected, possess an immunity from subsequent attacks. 



These are the general conclusions which the Commission 

 has deemed itself authorised to draw from their experiments. 

 The absolute proportion of animals which become affected or 

 escape the disease, or of those which die and recover as a 

 general rule, cannot be deduced from the foregoing experi- 

 ments, which, for such a purpose, are too limited. The 

 Commission simply states the numbers resulting from their 

 experiments. From these it transpires that 45 of the animals 

 became severely affected with pleuro-pneumonia, and 21 per 

 cent, took the disease slightly, making in the whole 66 per 

 cent, which were more or less severely attacked. 84 per cent, 

 remained free from any malady. The proportion of animals 

 which re-acquired their wonted appearance of health amounted 

 to 83 per cent, whereas 17 per cent, died. 



If, therefore, we are asked, What is the cause of this disease? 

 we can reply in one word, Contagion; and the many accessory 

 causes tend simply to increase or to mitigate the severity of 

 the plague, not to induce it. Thus 



Firstly, We can shew the most sceptical on this point 

 filthy town dairies which have been perfectly free from the 

 disease when it has been most severe in the large towns, and 

 the health of these dairies could only be accounted for by the 

 judgment exercised in making the purchases. 



Secondly, The disease, like all other plagues and malignant 

 fevers, attacks more readily and more severely animals at the 

 period of parturition, or during lactation. This is one reason 

 which accounts for the greater prevalence of the disease 

 amongst dairy stock. 



Thirdly, The animal introduced into a healthy stock, and 

 which carries the disease, may be in perfect health appa- 

 rentlv, and in good condition. It usually has a cough; but a 



