92 ALBUMINOUS MATTERS. 



the case of the cartilages, however, this substance is termed chondrine, 

 from the source from which it is derived. Chondrine corresponds with 

 gelatine in most of its characters, but differs from it in being precipitated 

 from its watery solution by both acetic acid and lead subacetate. It 

 rotates the plane of polarization to the left 213.5. 



Elasticine. 



The fibres of all the yellow elastic tissues, as that in the middle coat 

 of the larger arteries, the elastic ligaments of the spinal column, and the 

 ligamentum nucha3, mainly consist of a homogeneous substance which 

 possesses all the physical properties of the fibre itself, and is furthermore 

 distinguished by its extremely refractory nature toward most chemical 

 reagents. It is obtained by boiling the elastic fibres successively with 

 alcohol, ether, water, acetic acid, dilute soda solution, and dilute hydro- 

 chloric acid. The elasticine is thus purified from other ingredients, but 

 is not itself soluble in either of the above reagents. It is not converted 

 into gelatine even by long boiling ; and it is dissolved, but, at the 

 same time, decomposed, only by the concentrated acids and alkalies. 

 The slender elastic fibres mingled with connective tissue, and the sarco- 

 lemma of the striped muscular fibres, are probably composed of the 

 same substance. 



Keratine. 



Under this name is known the exceedingly resisting and indestruc- 

 tible substance of the hair, nails, epidermis, feathers, and all horny 

 tissues. It is unaffected by boiling with alcohol, ether, water, and the 

 dilute acids. By continuous boiling in a Papin's digester at 150 (302 F.) 

 it is liquefied and partly decomposed. It is distinguished from the 

 preceding substance by containing sulphur as an ingredient, which is 

 not present in elasticine. Keratine, accordingly, when decomposed by 

 boiling under pressure or with concentrated alkalies, gives rise to hydro- 

 gen sulphide vapors. 



It is evident that the albuminous substances, under different forms, 

 constitute a large and important part of the mass of the body ; and as 

 they are during life in a constant state of active alteration, they require 

 for their maintenance an abundant supply of similar ingredients in the 

 food. All highly nutritious articles of diet contain more or less of 

 these substances. According to the estimates of Payen, which corre- 

 spond very closely in their gross results with our own observations, an 

 adult man requires a daily supply of about 130 grammes of albuminous 

 matter to provide for the wants of the system ; and this quantity is 

 actually contained in the food consumed. 



But although nitrogenous matter is thus abundantly supplied to the 

 system from without, yet the particular kinds of albuminous substances 

 characteristic of the various tissues and fluids are formed within the 

 body in the process of digestion and assimilation, by transformation of 



