TRUE NUCLEINS. Ill 



min, proteoses, and finally peptones. Trypsin acts as does pepsin, 

 except that the reaction must be alkaline, not acid, the products 

 being alkali-albumin, proteoses, and peptones. 



In speaking of the ash produced when fibrin is burnt, Schafer 

 says that it invariably contains lime, but not more than other pro- 

 teids, nor more than the fibrinogen from which it is formed. This 

 fact completely disposes of the theories of coagulation which as- 

 sume that fibrin is merely a combination of fibrinogen with lime, 

 such as those of Freund, Arthus, Pekelharing, and Lilienfeld. 



Myosinogen. This globulin occurs in muscular tissue, and 

 in the condition called rigor mortis coagulates, and in this condi- 

 tion is myosin or muscle-clot. A similar change, heat-rigor, occurs 

 when muscle is heated, coagulation taking place when the temper- 

 ature reaches 47 to 50 C. ; and a second coagulation at 56 C. 

 This is due to the fact that there are two globulins : paramyo- 

 sinogen which coagulates at the lower, and myosinogen at the 

 higher temperature. 



I/actoglobulin. This proteid is found in cows' milk in such 

 minute quantity that it has escaped the analyses of excellent 

 chemists. 



Crystallin. The proteid matter of the crystalline lens is 

 crystallin, and exists in that structure to the amount of 34.93 per 

 cent. Two varieties of crystallin are described : a-crystallin and 

 /9-crystallin, differing in composition, specific rotatory power, and 

 coagulation-point. The former is more abundant in the outer 

 portion of the lens ; the latter, in the inner. 



NUCLEOPROTEIDS. 



These substances are composed of nucleins and proteids, and 

 occur in the nuclei and protoplasm of cells. Nucleins have been 

 obtained from the nuclei of pus-corpuscles, spermatozoa, yolk of 

 egg, yeast, liver, brain, and cows' milk. The term nucleins is used 

 rather than nuclein because there are several of these substances, 

 differing in solubility and chemical composition. They are divided 

 by Hoppe-Seyler into three groups : 



1. Nucleins which consist only of nucleic acid, whose formula 

 is not definitely known, but is approximately C 40 H 54 N 4 O 17 (P 2 O 5 ) 2 . 

 Indeed, nucleic acid is itself probably not a single substance, no 

 less than four having been found by investigators. This acid 

 does not give the reactions of proteid, but is characterized by its 



freat affinity for basic dyes, such as methyl-green (see Karyo- 

 inesis, p. 28). Nucleins of this group occur in spermatozoa. 



2. True Nucleins. These occur in the nuclei of cells, and 

 on decomposition yield proteid, xanthin bases (hypoxanthin, 

 xanthin, guanin, adenin), and phosphoric acid. The true nucleins, 

 which contain the most nucleic acid, are obtainable from the 



