32 PROTEIDS. 



myosin is dissolved in NaCl or MgS0 4 (10 and 5 p.c. respectively) 

 it yields a renewed clot on mere dilution with water. 



According to .N'usse l inyosin constitutes the anisotropous substance 

 (see above 56) of the unaltered muscle-fibre, and the activity of con- 

 traction is inversely proportional to the amount of this substance 

 which is present in the fibres of different animals. 



Globulins to which the name of myosin is applied are described 

 as occurring in vegetable protoplasm 2 and in the cells ofThi' 



Myosin is readily digested by pepsin, more slowly by trypsin. 

 The primary products arising from the digestive action oF the 

 former enzyme have been studied by Kiihne and Chittenden. 4 



6. Globin. 



When haemoglobin is allowed to undergo decomposition spon- 

 taneously by exposure to the air an. insoluble proteid is bbtanied 

 of which very little is known, but to which the name of globin 

 was given by Preyer. 5 It appears to be perhaps an outlying 

 member of the globulin class of proteids, but unlike a true glob- 

 ulin is scarcely soluble in dilute acids and imperfectly soluble 

 in alkalis and solutions of sodium chloride. It is converted into 

 acid and alKaii-albumm by the action of strong acids and alkalis 

 respectively, and is stated to yield no trace of ash on incineration 



CLASS IV. Fibrin. 



This proteid is ordinarily obtained by ' whipping ' blood with 

 a bundle of twigs until clotting is complete ; the fibrin which 

 adheres to the twigs is then washed in a current of water until 

 all the haemoglobin of the entangled corpuscles is removed and it 

 is now quite white. The washing is greatly facilitated if the 

 fibrin is very finely chopped before it is washed, and if it is fre- 

 quently kneaded and squeezed with the hand during the washing. 

 In this way it may be obtained quite white in a few hours. The 

 washing is also much facilitated if the blood is mixed with an 

 equal bulk of water before it is whipped. It is obvious that fibrin 

 prepared by the above method must be in an extremely impure 

 condition, for it contains a not inconsiderable admixture of the 



1 "Anat. u. Physiol. d. Muskelsubst." Leipzig, 1882. BioJ. Centra/It. Bd. n. 

 (1882-3), S. 313. Zt. f. phi/siol. Chem. Bd. vn. (1882), S. 124. 



2 Weyl, Zt. phi/Sid^ Chem. Bd. i. (1877), S. 96. 



3 Pldsz, Pfliiger's Arch. Bd. vu. (1873), S. 377. 



4 Zt.f. Biol. Bd. xxv. (1889), S. 358. See also Chittenden and Goodwin, Jl. of 

 PKifsiol. Vol. xii. (1891), p. 34. 



' 5 "Die Blutkrystalle," Jena, 1871, S. 166. 



