Disease amonrf Lamhs. 291 



constitution on the digestive orcrans) in the improved breed than 

 in the wikler and hardier races. It is also essential that these 

 principles should be given in such a condition that they can be 

 assimilated by the nutritive organs of the animal to which they 

 are supplied according to its requirements; and the capacity lor 

 assimilating food will further vary at different ages and in dif- 

 ferent breeds. It is then, I repeat, to some defect in the nitro- 

 genous element supplied in the food that I attribute the enormous 

 losses sometimes sustained among lambs in the autumn season. 



In proof that a good supply of nitrogen is essential to animals, 

 especially during their growth, it may be shown that all parts oi 

 the body which possess a decided shape contain nitrogen ; hence 

 we may infer that this element has to perform certain important 

 functions in reference both to the formation and nutrition of the 

 tissues. The most convincing experiments and observations have 

 proved that this nitrogen can be derived from no other source 

 than the food ; consequently a larger supply is needed in youth, 

 when the frame has to be built up, than in mature age, when the 

 existing organism has only to be maintained. If we refer to 

 the constitution of milk, the natural provision for the young 

 animal, we find that in it the hydro-carbonaceous principle bears 

 to the nitrogenous principle the proportion of only two to one, 

 whereas in the food of adults it generally bears the proportion of 

 six to one ;. and thus, whilst on the one hand science has led us to 

 the conclusion that more than an average supply of nitrogen is 

 required to build up the frame, on the other it indicates that a 

 larger supply is provided by nature for that end. 



Breed has some effect also in the production of this disease. 

 Short-woolled sheep will thrive upon dry arid pastures, exposed 

 to the inclemency of winter and the drought of summer ; but the 

 sheep principally kept upon the forest land of this neighbourhood, 

 though originally of this class, have, for the sake of improving 

 the clip of wool, been so repeatedly crossed with Leicesters or 

 Lincolns, that they require a better supply of food than the hardier 

 and purer original breed. Leicester sheep have a greater develop- 

 ment of lax, extensible cellular tissue in the soft solids ; their 

 vascular and nervous systems are more sluggish and inactive; they 

 have also a greater tendency to fatten, but are incapable of bearing 

 exposure or hardship. 



Mr. Karkeek, in his ' Essay on Fat and Muscle,' says, " that 

 in proportion as an animal increases in fat will the organs of 

 nutrition become diminished in size ; it follows that by pursuing 

 the system of breeding from fatted animals, or those having a 

 tendency to iaXien^ function must react upon organisation, and at 

 last those qualities become not only increased but fixed in the 

 race." Therefore, in the continued endeavours to produce a breed 



