CHEMICAL BASIS OF THE ANIMAL BODY. 873 



sodic chloride, and the fibrinogen finally purified by being several times dissolved in 

 and reprecipitated by sodic chloride. 



There is no proof that the whole of the substance thrown down by carbonic 

 anhydride from diluted blood-serum is fibrinoplastic ; indeed we know that a true 

 globulin devoid of fibrinoplastic properties may be prepared from serum. 1 Weyle 2 

 considers that there is only one globulin in serum, which he characterizes by the 

 name of " serum-globulin," and regards h'brinoplastin as a mixture of this body 

 with a portion of fibrin-ferment. We know for certain (see p. 28) that the whole 

 of the n'brinoplastic precipitate, used to cause the coagulation of a fibrinogenous 

 fluid, does not enter into the composition of the fibrin produced ; we also know that 

 such a precipitate may lose its fibrinoplastic powers without any marked change in 

 its general reactions. It would seem advisable, therefore, to speak of the deposit 

 produced by carbonic anhydride in dilute serum, or by saturation with sodic chloride 

 in undiluted serum, as globulin, and to distinguish it as fibrinoplastic globulin when 

 it is able to give rise to fibrin. Fibrinogen similarly might be spoken of as fibrin- 

 ogenous globulin. Tl>e name crystallin, rather than globulin, might then be given 

 to the substance obtained from the crystalline lens. 



4. Myosin. 



This is the substance which forms the chief proteid constituent of dead, rigid 

 muscle ; its general properties and mode of preparation have been already 

 described at p. 84. In the moist condition it forms a gelatinous, elastic, clotted 

 mass ; dried, it is very brittle, slightly transparent, and elastic. From its solution 

 in sodic chloride it is precipitated, either by extreme dilution or by saturation 

 with the solid salt. When precipitated by dilution and submitted to the pro- 

 longed action of water, myosin loses its property of being soluble in solutions of 

 sodic chloride. 3 The sodic chloride solution, if exposed to a rising temperature, 

 becomes milky at 55 C. , and gives a flocculent precipitate at 60 C. This precip- 

 itate is, however, no longer myosin, for it is insoluble in a 10 per cent, sodic chloride 

 solution, and does riot, until after many days' digestion, yield syntonin on treat- 

 ment with hydrochloric acid (0.1 per cent.). It is. in fact, coagulated proteid (see 

 Class V.). 



Myosin is excessively soluble in dilute acids and 'alkalies. Advantage may be 

 taken of its solubility in the former to extract it from muscles. 4 But if the 

 reagents are at all concentrated, myosin undergoes in the act of solution a radical 

 change, becoming in the one case acid-albumin or syntonin, in the other alkali- 

 albumin (Class II.). 



Like fibrin, it can in some cases decompose hydrogen dioxide, and oxidize guaiacum with for- 

 mation of a blue color. 



5. Vitellin. 



As obtained from the yolk of egg, of which it is the chief proteid constituent, 

 vitellin is a white granular body, insoluble in water, but very soluble in dilute sodic 

 chloride solutions ; it surpasses myosin in this respect, for the solution may be easily 

 filtered. Its coagulation temperature is higher than that of myosin, lying, accord- 

 ing to Weyl, 5 between 70 C. and 80 C. Saturation with sodic chloride gives 

 no precipitate ; in this respect it differs from most other members of this class. In 

 yolk of egg vitellin is always associated with, and probably exists in combination 

 with, the peculiar complex body lecithin. 



Denis, and after him Hoppe-Seyler, have shown that vitellin before the treatment requisite to 

 free it from lecithin possesses properties quite different from other proteids. 



A theory has been advanced that vitellin is really a complex body like haemo- 

 globin, and on treatment with alcohol splits up into coagulated proteid and leci- 

 thin. When well purified it contains 0.75 percent, sulphur, but no phosphorus. 

 Dilute acids or alkalies readily convert it in its uncoagulated form into a member 

 of Class II. 



1 Kiihne and Eichwald, loc. cit. 2 LOC. cit. 



Weyl, Zeitschr. f. Physiol. Chem., Bd. i. (1878),- S. 77. 



Danilewsky, Zeitschr. f. Physiol. Chem., Bd. v. (1881), S. 158. 5 Qp. cit. 



