254 



BREEDING 



and the oxygenation of the blood be effected by the process of osmosis. 

 Tlius the placental union may be looked upon as representing an organ of 

 respiration as well as of nutrition. 



Growth and development continue from the stage at which the embryo 

 was left at the seventh week to the period when the embryo becomes 





W^i,, ^ 



\ 



Fig. 542.— Foal about Fourth Month 



the foetus, about the fourth month (fig. 542) all the organs then being 

 miniature representations of those of the animal when separated from the 

 mother by the act of parturition. 



A detailed account of every step in the further development of the 

 embryo would occupy more space than can well be allotted to the sub- 



