1018 AN AMERICAN TEXT-BOOK OF PHYSIOLOGY. 



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. 



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 gelatin- 

 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. 



Froteoses 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 gastric digestion are said to exist four 

 varieties of proteoses: (1) Dysproteose, insoluble in water and dilute NaCl solutions, (2) 

 hetero-proteose, insoluble in water and soluble in NaCl solution, (3) proto-proteose, soluble 

 in water and in NaCl solution, (4) deutero-proteose, which is also soluble in water and in 

 NaCl solution, but is distinguished by the fact that while the first-named three are pre- 

 cipitated by saturating the neutral solution with NaCl, deutero-proteose is only partly 

 precipitated, the rest coming down on addition of an acid. Proteoses are converted into 

 amphopeptones, a mixture of hemi- and antipeptone. According to Kuhne proteid con- 

 sists of a hemi- and an anti- group, which separate into distinct hemi- and anti- bodies in 

 proteolysis. Of the final products, hemi- and antipeptone, only the former yields leucin 

 and tyrosin in tryptic proteolysis. This is the only radical difference between the two 

 peptones, hence hemipeptone has never been isolated. 



Coagulated Proteids. These are insoluble in water, salt-solutions, alcohol, dilute 

 acids and alkalies, but soluble in strong acids and alkalies, pepsin-hydrochloric acid, 

 and alkaline solutions of trypsin. The chemical or physical change which is effected in 

 coagulation of proteid is unknown. 



Combined Proteids. These consist of proteid united to non-proteid bodies such as 

 hsemochromogen, carbohydrates, and nucleic acid. 



Chromo-proteids. These are compounds of proteid with an iron- or copper-contain- 

 ing pigment, like haemoglobin, which has already been described. Histohcematins are 

 iron-containing pigments found especially in muscle. That which is found in muscle is 

 called myohaematin, and resembles haemochromogen somewhat in its spectroscopic appear- 

 ance, and is believed to be present in two forms corresponding to haemoglobin and oxyhaemo- 

 globin. It has been regarded as an oxygen-carrier to the tissues. Among the inverte- 

 brates the blood often contains only white corpuscles with sometimes a colored plasma. 

 Thus the blood-serum of the common earth-worm contains dissolved haemoglobin, that 

 of some other invertebrates a green respiratory pigment, chlorocruorin, whose charac- 

 terizing component seems similar to haematin ; hcemerythrin occurs in the pinkish corpus- 



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. 



