2iy Microscopical Researches on (he Conformity of 



5. Crystalline lens. — The fibres of the crystalline lens spring from cells, 

 discovered by Werneck (See the Archives of Meyer Ahrens^ 1838, 269), 

 In the crystalline lens of the common fowl, after eight days incubation, 

 no fibres are yet found, but only rounded, pale cells, some of which con- 

 tain a nucleus. At a more advanced period, a few cells of larger dimen- 

 sions enclose one or two smaller nuclei. In the embryo of a sow, about 

 3.\" long, the greater part of the fibres of the lens are already formed ; a 

 portion is still unfinished, and a great number of cells likewise exist await- 

 ing their change. The completed fibres form a ball in the centre of the 

 kiitille. The fibres closest to each other are hollow elongations of the 

 g lobules. At a later period, these fibres become garnished with dentated 

 edges, as is seen in the dentated cells of plants. 



Third Class. 1. Cartilage. (See page 22). 



Teeth. — The enamel of a tooth not yet developed, when treated by a 

 weak acid, preserves the same structure. The inner surface of the ena- 

 njclling membrane which surrounds the crown of the tooth is formed of 

 short fibres, with six faces, situated vertically, so that each fibre of the 

 cuamelling membrane corresponds to a fibre of enamel : they appear to 

 consist of elongated cells. In a recent state they contain a nucleus with 

 a nucleolule; above them are situated rounded cells, adhering to the 

 cnauiclling membrame, which is no doubt the young state of the former. 

 The enamelling fibres, properly so called, are probably separated from 

 the enamelling membrane, in order that they may become soldered to the 

 enamel already formed, and ossify along with it. 



Tlie proper substance of teeth originates from the fibres among which 

 the dentary canals occur. The pulp of a tooth is composed at the sur- 

 face of cylindrical cells, with a nucleus and nucleolules, and of round 

 cells in the interior. Schwann thinks that the superficial fibres change 

 into the substance of the tooth. 



Fourth Class. 1. Cellular tissue.— The origin of the cellular tissue is 

 the cytoblastema without structure. It produces in its interior rounded 

 cells with a nucleus, which change into fibrous fusiform cells, enclosing 

 a round or oval corpuscle, in which one or two dark points may be dis- 

 tinguished. The nucleus rests against the wall of the cell. These cells, 

 by becoming narrow at the extremities, change into fibres. The points 

 of the fusiform cells give rise to fibres which sometimes emit branches, 

 and terminate by becoming transformed into a fascicle of extremely deli- 

 cate fibres. The development takes place in the following manner : the 

 division of the two principal fibres, which go ofi* from the body of the 

 cell in a bundle of smaller fibres, approaches more and more to that body ; 

 so that, at a later period, the latter becomes the point where the fibrous 

 fascicle takes its departure ; at a still later period, the fibrous fascicle 

 springs directly from the nucleus; lastly, the cellular body divides wholly 

 into fibres, and the nucleus rests naked on a fascicle of these fibres. 

 The latter arc probably hollow. 



