578 AN AMERICAN TEXT- HOOK OF PHYSIOLOGY. 



Fibrin yields a carbohydrate radicle which appears in deutero-proteose B and subse- 

 quently in peptone A. 1 The primary proteoses are believed to break np into secondary 



proteoses, such as deutero-proteose A and deutero-proteose C. and perhaps others, and 

 these secondary proteoses maybe converted into peptones, although gastric digestion will 

 not convert some deutero-proteoses into peptone. 2 Egg albumin and other proteids 

 yield similar products. The whole process of proteolytic cleavage has been compared 

 with the hydrolytic cleavage of starch into dextrins and sugars. According to Kiihne, 

 proteid consists of a hemi- and an anti- group, which separate into distinct hemi- and 

 anti- bodies in proteolysis. Of the final products, hemi- and anti-peptone, only the former 

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

 the two peptones, hence hemi-peptone has never been isolated. Kutscher 3 denies the 

 existence of anti-peptone and shows that prolonged tryptic proteolysis almost completely 

 transforms proteid into amido bodies. 



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 

 hgemochromogen, 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 myohsematin, and resembles bsemochromogen 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 hsematin ; hcemerythrvn occurs in the pinkish corpus- 

 cles of Sipunculus, while the blood of crabs, snails, and other animals (mollusks and 

 arthropods) is colored blue by a pigment, hcemocyanin, which contains copper instead of 

 iron. 



Glyco-proteids. — These consist of proteids combined with a carbohydrate. They are 

 insoluble in water, but soluble in very weak alkalies. On boiling with dilute mineral acids 

 they yield a reducing substance. 



Mucin* are found in mucous glands, goblet cells, in the cement substance of epithelium 

 and in the connective tissues. Of the nearly related mucoids may be named colloid, a sub- 

 stance appearing like a gelatinous glue in certain tumors; pseudo-mucerid, the slimy body 

 which gives its character to the liquid in ovarian cysts; and chondro-mucoid, found as a 

 constituent of cartilage. On boiling chondro-mucoid with dilute sulphuric acid it yields 

 acid-albuminate, a peptone substance, and chondroitic acid. The last is a nitrogenous 

 ethereal sulphuric acid, yielding a carbohydrate on decomposition, and found preformed in 

 every cartilage * and in the amyloid liver. 5 It is. of course, not a proteid. Amyloid is 

 similar to chondro-mucoid, and may be identical with it. Tt is said to consist of 

 chondroitic sulphuric acid in combination with proteid. 6 and yields proteid and phosphoric 

 acid on decomposition. 



1 Pick : Zeitsehrifijur •physiologwehe Chemie, 1899, Bd. 28, S. 219. 



a Folin: Ibid., 1898, Bd. 25, S. 1 52. 



B Die Endprodukle der Trypsrinverdauung, Strassburt;, 1899. 



4 Morner: Zeitschriftfur physiologische Chemie, 1895, Bd. 20, S. 357. 



b Odili : Archiv fiir exper. Pathologic und Pharmakologie, 189-1, Bd. 33, S. 376. 



6 Krawkow : Ibid., 1897, Bd. 40, S. 195. 



