618 BRAIN AND NERVES. 



great difficulty by pepsin-hydrochloric acid or trypsin solution, but are 

 soluble in dilute acids and alkalies in the warmth. Membranin of the 

 capsule of the lens contains 14.10 per cent N and 0.83 per cent S, and is 

 a little less soluble than that from DESCEMET'S membrane. 



The principal mass of the solids of the crystalline lens consists of 

 proteins, whose nature has been investigated by C. M6RNER. 1 Some of 

 these proteins dissolve in dilute salt solution, while others remain 

 insoluble in this solvent. 



The Insoluble Protein. The lens fibers consist of a protein sub- 

 stance which is insoluble in water and in salt solution and to which 

 MORNER has given the name albumoid. It dissolves readily in very dilute 

 acids or alkalies. Its solution in caustic potash of 0.1 per cent is very 

 similar to an alkali-albuminate solution, but coagulates at about 50 

 C. on nearly complete neutralization and the addition of 8 per cent NaCl. 

 Albumoid has the following composition: C 53.12, H 6.8, N 16.62, and 

 S 0.79 per cent. The lens fibers themselves contain 16.61 per cent N 

 and 0.77 per cent S. The inner parts of the lens are considerably richer 

 in albumoid than the outer. The quantity of albumoid in the entire 

 lens amounts on an average to about 48 per cent of the total weight of 

 the proteins of the lens. 



The Soluble Protein consists, exclusive of a very small quantity of 

 albumin, of two globulins, a- and p-crystallin. These two globulins differ 

 from each other in this manner: a-crystallin contains 16.68 per cent N 

 and 0.56 per cent S; jS-crystallin, on the contrary, 17.04 per cent N and 

 1.27 per cent S. The first coagulates at about 72 C. and the other at 

 63 C. Besides this, j8-crystallin is precipitated from a salt-free solu- 

 tion with greater difficulty and less completely by acetic acid or carbon 

 dioxide. These globulins are not precipitated by an excess of NaCl at 

 either the ordinary temperature or 30 C. Magnesium or sodium sul- 

 phate in substance precipitates both globulins, on the contrary, at 30 C. 

 These two globulins are not equally divided in the mass of the lens. The 

 quantity of a-crystallin diminishes in the lens from without inward; 

 j8-crystallin, on the contrary, from within outward. 



A. JESS 2 has found that the different proteins of the crystalline lens 

 behave differently with ARNOLD'S protein reaction with sodium nitro- 

 prusside (page 100). The albumoid gives negative results with this 

 reagent. The a-crystallin gives it faintly, while the /3-crystallin gives a 

 strong reaction. The absence of this reaction, as observed by WEISS 

 in senile cataract, is connected with the fact as JESS has shown by his 

 investigations on the senile cataract in oxen, that the crystallin con- 



1 Zeitschr. f . physiol. Chem., 18. This contains also the pertinent literature. 

 Zeitschr. f. Biol., 61. 



