CASEIN FEE-EXISTS IN BLOOD. 231 



founded on the data furnished by the tables of the constitution of blood and 

 of milk respectively, will show that there is at any moment a sufficient 

 supply of fatty matters in the blood to furnish two thirds of the diurnal 

 amount of milk. It does not seem, therefore, philosophical, under these 

 circumstances, to impute to the mammary gland a power of forming but- 

 ter. It doubtless obtains that substance directly from the blood ; and it 

 may be that those bodies which are conceived of as cells, and which are 

 supposed to arise in the lobules of the gland in successive broods, which 

 run a rapid living career, coming into existence, reaching maturity, dying 

 and deliquescing with incredible rapidity, are, in reality, nothing more 

 than oil globules which have coated themselves over with a cyst of coag- 

 ulated casein, as in Ascherson's experiment, or just as they become coat- 

 ed with a similar film immediately on passing from the intestine into the 

 lacteal vessels ; and this, accordingly, is the opinion I entertain of their 

 nature. 



Next of the casein. There has been much controversy among chem- 

 ists respecting the existence of casein as a normal ingredi- Reasons for in- 

 cut in the blood. Theoretically there does not appear any jSbSl? > 

 solid reason for denying that it may be one of those constit- blood, 

 uents, considering the analogy of constitution which it shows with albu- 

 men. The evidence is much more distinct and positive in the case of 

 puerperal blood, and is greatly strengthened by the recognized tendency 

 to the occurrence of kiestine in the urine during gestation. This sub- 

 stance, to which much attention has of late been devoted, makes its ap- 

 pearance in such urine as a pellicle or membrane, which gradu- 

 ally increases in thickness. It is not commonly seen before 30 

 hours after the urine is passed, nor later than the eighth day. Though 

 sometimes appearing at an earlier period of gestation, it is more frequent 

 in the seventh, eighth, or ninth months. The fact is not without signifi- 

 cance for our present purpose, that it may reappear in the urine after par- 

 turition if any thing occurs to check the secretion of milk. Moreover, 

 Prout noticed it in the urine of a delicate child which was fed chiefly on 

 milk. An examination of it shows that kiestine is composed of casein, a 

 butyric fat, and the phosphate of magnesia. Such a constitution betrays 

 at once its relation to the secretion of the mammary gland. 



Lehmann, who inclines to the belief that kiestine is nothing else but 

 the formation of crystals of triple phosphate and fungoid and confervoid 

 growths, which take place when the urine becomes alkaline, admits that, 

 unless it has been the basic albuminate of soda which has been mistaken 

 for it, casein does occasionally occur in the urine. From the acknowl- 

 edged fact that the acid interstitial juice of muscle fibre contains casein, 

 there can not be any doubt, I think, that that substance must pre-exist 

 in the blood. 



