90 THE LAWS OP ORGANIC 



their appearance in the space of a week or a fort- 

 night more vigorous and sleek but, as soon as 

 the thermometer, in the situation in which they 

 were placed, was as low as 35 or 40 degrees, they 

 presented marked alterations. They crept along 

 as if afraid to expose a large surface of the body 

 to the cold, the sleekness vanished, and the 

 spine soon shewed an unusual prominence, and, 

 when these signs were evident a nightly morta- 

 lity lessened the stock. For some time I attri- 

 buted their haggard and consumptive aspect 

 to disease ; but after reflecting on the influence 

 of cold in modifying the qualities of the blood 

 and its distribution, I was naturally led to 

 regard the assimilative powers of the system 

 as affected by these changes ; and, believing 

 this opinion to be correct, I endeavoured to 

 obviate former consequences by the application 

 of principles deduced from the consideration of 

 their cause. When the days in winter were par- 

 ticularly severe, I placed the young and sickly 

 in a large box kept in the room with the others ; 

 and, by pursuing this plan, I preserved their 

 number and increased their vigour. It is scarce- 

 ly possible to convey an idea of the difference I 

 perceived, in point of liveliness and health, be- 

 tween those subject to a temperature of 75 in a 

 confined place, and those exposed to 35 or 40 

 in a small room. 



I have not made any experiments on the most 



