Breeding Power and Sterility. 117 



but these can only be used in proportion to the quantity 

 of oxygen contained in the artery circulation. Hence the 

 7iaiHral proportion of oxygen supplied by breathing is in- 

 dispensable alike to circulation of the blood and the nutri- 

 tion of the tissues. 



While breathing vitalizes or gives life to the blood, it is 

 a dual and reciprocating process, purifying by the exhala- 

 tion of poisonous and dead matter, while it vivifies and 

 vitalizes by the inhalation of oxygen. Hence the vital 

 quality of the blood depends mainly on breathing ; and 

 the natural proportion of oxygen can only be supplied by 

 the natural extent oi breathing, which again depends upon, 

 and can only be according to, tlie natural degree of mus- 

 cular motion, or sufficient regular exercise. 



The various vital secretions cannot, of course, be ex- 

 tracted from the crude, unassimilable portion of the blood, 

 but are derived from its vital assimilable qualities, which are 

 used in proportion to the oxygen, which causes it to circu- 

 late. Hence the quantity of the digestive juices, and of the 

 primary breeding organisms — the spermatozoa in the male 

 and the ova in the female — cannot exceed a small and 

 strictly limited proportion to the vital elements of the 

 blood they are formed from. .So tliat success, even in 

 primary breeding itself, depends upon exercise and breath- 

 ing, which both insure its circulation, and give life as 

 well as motion to the blood. 



The nutritive proportion of the blood probably com- 

 prises not far from half its' entire bulk; the other moiety 

 serving to increase the size of the blood-vessels, and the 

 extent of their surface, so increasing the area of secretive 

 action, and maintaining the size of the blood channels 

 generally. 



Heat increases with the increase of blood, in the region 

 of the ovaries, which, by its greater extent, brings on 

 Coupling-heat ; but we cannot infer from this that the vital 



