294 PRINCIPLES OF STOCK-BREEDING. 



in the process of development, has been made use of 

 in the classification of animals : as in birds, for exam- 

 ple, those with webbed feet are placed lower in the 

 scale of organization, the developmental process not 

 having proceeded so far as in those with separate toes. 



In the higher animals, digits that adhere or are 

 connected by a membrane represent the embryonic 

 type that has been retained through defective devel- 

 opment. The lamb mentioned above, that presented 

 a fancied resemblance to a rabbit in the form of its 

 feet, was undoubtedly an instance of arrested de- 

 velopment. 



" The foetus in utero, even at early periods of its 

 development, is liable to a large number of organic 

 alterations, and even to lose its life, in consequence of 

 inflammation attacking the uterus of the mother, the 

 foetal appendages, or its own system. From such 

 causes arise a variety of pathological changes in the 

 foetus, as atrophy, arrest of development, amputation 

 of limbs, and many other affections." 1 



The particular part of the foetus affected by disease 

 is undoubtedly determined by the same general con- 

 ditions that determine the seat of disease after birth, 

 among which may be enumerated irregularities of the 

 circulation, producing local congestions or inflamma- 

 tion, hereditary predisposition to disease of particular 

 organs, mechanical injuries, and specific diseases com- 

 municated by the mother, as small-pox, scarlet fever, 

 measles, etc. 2 



1 Montgomery, " Cyclopaedia of Anatomy and Physiology," article 

 " Foetus," vol. ii., p. 330. 

 9 Ibid., p. 333. 



