THE LYMPHATIC AND MUCOUS SECRETIONS 903 



The most important differences may be briefly summarized as fol- 

 lows: 



(a) Appearance. Cow's milk is white in color and opaque, while human milk 

 is more translucent and possesses a yellowish or bluish hue in accordance with its 

 concentration. 



(6) Reaction. Cow's milk is acid, while human milk is alkaline, 



(c) Specific gravity. Cow's milk: 1.030-1.035; human milk: 1.024-1.035, 



(d) Character of the curd. Rennet produces with cow's milk a dense and firm 

 coagulum which is not easily digested, while human milk yields under the same 

 circumstances a light, flocculent and easily digestible clot. 



(e) Histological character. The fat-globules of cow's milk are invested by a 

 relatively thick albuminous envelope. 



(/) Bacteriological character. Human milk is in a practically sterile condition 

 when withdrawn from the breast. 



These differences in the chemical composition and reaction must 

 first be removed by diluting cow's milk to reduce the casein and by 

 adding to it cream and milk-sugar, making the whole alkaline in re- 

 action. The danger of microbic infection of cow's milk may be obvi- 

 ated by pasteurization, i.e., by subjecting the milk to a temperature of 

 167-175F. which sterilizes it, but does not impair its nutritive value. 

 The following formula may be employed as a sample : 



Top milk 5 drams 



Water 5 drams 



Lime water 1 dram 



Sugar of milk 20 grains 



But this "humanized" cow's milk cannot be regarded as a perfect 

 substitute for natural mother's milk. Undoubtedly, there are also 

 certain other differences present which the chemist has not detected as 

 yet. As one of these might be mentioned the qualitative differences 

 between the caseinogen of different types of milk. 



CHAPTER LXXVII 

 THE LYMPHATIC AND MUCOUS SECRETIONS 



The Spleen. Since this organ possesses the characteristics of 

 lymphatic tissue and has not been proved to furnish an internal se- 

 cretion, it may properly be considered under the heading of the lym- 

 phatic glands. It is, of course, a ductless 9rgan and belongs to the 

 group of the hemal bodies which are distinguished from the ordinary 

 lymphatic glands by their red color and by the fact that their sinuses 

 contain only blood. Histologically it is of importance for us to re- 

 member that it is enveloped by a capsule of fibrous tissue, containing 

 elastic fibers and smooth muscle cells. Numerous septa or trabeculae 

 extend from its inner surface into the interior of the organ which they 



