THE CHEMISTRY OF THE ANIMAL BODY. 577 



c Casein ; 

 ^ 1. Those yielding para-nuclein < Pyin ; 



Nudeo-proteids \ ' Vitdlin. ^ 



o T , • 1V , l • i Nucleo-histon ; 



v 2. Ihose yielding true nuclei n < - „ , . ' 

 J I Gell-nuclein. 



Phospho-glyco-proteids. Helico-proteid. 



Albuminoids. 

 Collagen (gelatin). 

 Elastin. 

 Keratin and Neurokeratin. 



Albumins. — Bodies of this group are soluble in water and precipitated by boiling, or 

 on standing with alcohol. Serum-albumin is the principal proteid constituent of blood- 

 plasma, while lacto-albumin and myo-albumin are similar bodies found respectively in 

 milk and muscle. 



Globulins. — These are insoluble in water, but soluble in dilute salt-solutions. They 

 are coagulated on heating. If blood-serum be dialyzed with distilled water to remove the 

 salts present, serum-globulin formerly held in solution separates in flakes. Fibrinogen and 

 serum-globulin are in blood-plasma and the lymph. Myosin is the principal constituent 

 of dead muscles ; in the living muscle myosin is said to be present in the form of myosin- 

 ogen. Myoglobulin in muscle is akin to serum-globulin in plasma. Paramyosinogen in 

 muscle is characterized by the low temperature at which it coagulates (+47°). Cell- 

 globulin is also found in the animal cell. 



The globulins of vegetable cells are interesting as having been obtained in well-defined 

 crystalline form and in great purity of composition. 1 These are not generally coagulable 

 by heat, and indeed vegetable proteids show many points of divergence from those of the 

 animal. 



Osborne 2 finds that solutions of pure crystalline edestine obtained from plants take up 

 hydrochloric acid inexact chemical relations, forming the hydrochlorato or bihydrochlorate 

 of edestine. The simplest formula for edestine ( containing two atoms of sulphur) which can 

 be calculated gives a molecular weight of 7,138, twice which is 14,276. This latter molec- 

 ular weight exactly unites with one molecule of hydrochloric acid to form edestine 

 hydrochlorate. Osborne regards the many variations in similar L ' native " albumins as being 

 fundamentally caused by the quantity and quality of the acid or alkali with which they 

 unite. 



Albuminates. — If any of the above native animal proteids or any coagulated proteid 

 be treated with an alkaline solution, alkali albuminate is formed. In this way the alkali 

 of the intestine acts upon proteid. If hydrochloric acid acts on proteid. there is a gclatin- 

 ization and slow conversion into acid albuminate, a process accelerated by the presence 

 of pepsin. This takes place in the stomach. Both alkali and acid albuminates are in- 

 soluble in water, but both are soluble in dilute acid or alkali, without loss of individual 

 identity. 



Proteoses and Peptones. — These are bodies obtained from the digestion of proteids, 

 through a process of hydrolysis. They are non-coagulable by heat. If a mixture of pro- 

 teoses and peptones be saturated with ammonium sulphate the proteoses are said to be 

 precipitated, while true peptone remains in solution. The chemical identity of this true 

 peptone is still, however, to be established. In the gastric digestion of fibrin, proto- 

 proteose, hetero-proteose, and deutero-proteose B, arise as primary cleavage products. 8 



1 Osborne : Journal of American Chemical Society, 1894, vol. xvi., Nos. 9, 10; and other arti- 

 cles in the same journal by the same author. 



2 Op. efl.,1899, vol. 21, p. 48(3. 



3 Zunz, E. : Zeitschrift fiir physiologische Chemie, 1899, Bd. 28, S. 132. 



Vol.. I. — 37 



