348 MILK. 



extent in the latter as in the former, but that the potassium- 

 compounds and phosphates are present in the milk in even larger 

 quantities than in the blood-corpuscles : the preponderance of the 

 insoluble phosphates in the milk-ash has been already specially 

 noticed. But if we compare the soluble salts of the milk-ash with 

 those of the intercellular fluid and of the blood-corpuscles (as for 

 instance in the cow), it seems to follow as an almost necessary 

 consequence that the blood-corpuscles take part in the formation 

 of the milk, at all events in so far as the salts are concerned. 



As when we treat, in the third volume, of the process of secre- 

 tion, we shall fully enter into the histological and physiological 

 grounds which favour the view that there occurs a preliminary 

 remodelling of the substances to be conveyed by the blood to 

 the glands for secretion, we will here refer to that chapter, in 

 which, after reviewing all the chemical results which have been 

 described in the theory of the juices, the principle is fully 

 established, that the main constituents of all true secretions, like 

 those of the liver and the mammary gland, are first formed within 

 the glandular organs themselves. 



The physiological importance of the milk is so obvious, that it 

 would be altogether superfluous to enter fully into the subject : 

 but an accurate investigation of the influences which the individual 

 constituents of this secretion, which Nature itself has provided as 

 the type of normal food, exert on the infant, is of such great 

 physiological importance, that one of the fundamental laws of 

 physiological chemistry, the very turning point of the metamor- 

 phoses of the animal tissues generally, is based upon it. For this 

 reason we shall enter into a full consideration of this subject when 

 we treat of the theory of nutrition, and shall, therefore, postpone 

 all our remarks upon it for the present. 



SEMINAL FLUID. 



The seminal fluid, which is secreted by the testicles, and is 

 usually mixed with the prostatic fluid, is viscid, tenacious, opales- 

 cent, colourless (only becoming yellow on drying), of a peculiar 

 odour, considerably heavier than water, and of an alkaline reaction ; 

 when freshly discharged it is gelatinous, but after some time it 

 assumes a thin fluid consistence; a mucous sediment is formed 



