278 MANUAL OF HISTOLOGY. 



branches there exists no lens fibres, their place being occupied by a tena- 

 cious homogeneous mass. Thus we see that the organ in question is 

 divided by a system of partitions, springing with its layers from a central 

 space in the lens ; in that this substance can be followed through the 

 latter in the form of septa. 



The libres, therefore, form in each half of the lens some three or four 

 wedge-shaped pieces. 



This arrangement naturally determines the course of the fibres, and 

 makes it impossible that any one of them should actually reach both 

 poles. 



REMAKKS. 1. Beside German handbooks on histology and monographs, comp. 

 Bovman, Lectures on the parts concerned in the operations of the eye, etc., London, 

 1849 ; Th. Nunnely in the Journ. of Microsc. Science, 1858, p. 136. 2. These 

 broadened ends of the fibres of the lens may simulate when in transverse section a 

 flattened epithelium, without nuclei however. It was formerly supposed that there 

 existed between the lens and capsule a small quantity of a clear thick fluid, the 

 humor Morgagnii. This is not, however, present in the living eye, and is the result 

 of a post-mortem change, produced by the decomposition of the so delicately con- 

 stituted peripheral fibres and epithelium. The latter swells up before bursting into a 

 number of spherical globules (fig. 269, e). 



160. 



Turning now to the composition of the tissue of the lens, that of the 

 capsule, in the first place, is at present but insufficiently known. Th 

 latter gelatinises in acetic acid and solutions of the alkalies, without, how- 

 ever, becoming clouded or dissolved. Even after two days' boiling, also, 

 it is not converted into glutin. It offers prolonged resistance to the 

 action of alkalies, but is, on the other hand, gradually dissolved in the 

 mineral acids (Mensonides). Thus we have the reactions, to a certain 

 extent, of most of the transparent elastic membranes. On the other 

 hand, according to Strahl's statements, each capsule may be dissolved by 

 boiling for several hours in water, yielding a substance which does not 

 give, however, the reactions of glutin. 



The composition of the nuclei and walls of the lens fibres is not as 

 yet known. In their interior is contained a concentrated solution of a 

 peculiar and very unstable protein substance known as crystallin ( 12, 

 p. 1 7). Qwing to its close relationship to albumen, all reagents which cause 

 the latter to coagulate produce clouding in the tissue of the lens, and when 

 suitably employed may render the structure of the latter more distinct. 

 In this respect chromic acid has gained great repute. Besides this, the 

 lens contains a not inconsiderable proportion of fats, and, according to 

 older analyses, of extractive matters also. For the human lens Berzelius 

 obtained the following percentage, of 



Water, . . . . 58*0 



Protein matter, . * . . . . 35 '9 



Walls of the fibres, &c., remaining on the filter, . 2*4 



Extractive matters, . . . . . . 3*7 



The proportion of fats in the human lens was found to be 2 '06 per 

 cent. (Husson) ; among them cholestearin is present (Lolnneyer). The 

 amount of mineral constituents met with is only 0*35 per cent. The 

 clouding of the lens after death depends upon some change in composition 

 not yet understood. 



The specific gravity of this organ in the human being is, according to 

 Chenevix, 1*076 in the external layers, while that of the more denso 



