13 DR. G. THIN. 



every precaution had been taken to ensure that the sections 

 did not include the free surface of the cartilage. Individual 

 cells so seen are represented in Fig. 16. 



In regard to the cells usually seen in cartilage the fol- 

 lowing is to be added to the methods explained in the 

 text-books of histology : — An ordinary, not necessarily 

 very thin, transverse section is placed on a glass slip, in 

 aqueous humour or blood-serum, and cut in pieces by a sharp 

 knife, an oblique direction being given to the incisions. The 

 pieces are then sealed up in the ordinary way. To increase 

 the chances of success it is advisable to seal up a number of 

 preparations at one time. On the second day or afterwards 

 the obliquely cut edges should be carefully examined. 

 Supposing a preparation to have succeeded, in the oblique 

 edge of the incised surface the same protoplasmic clumps 

 that indicate the cartilage-cells in the rest of the section will 

 be found, but also there may be detected at intervals pear- 

 shaped protoplasmic masses lying free in such of the cellular 

 cavities as have been laid open by the incision. The pro- 

 jecting end of the protoplasm is irregularly round, but the 

 end Avhich is towards the section tapers to a fine prolongation, 

 which is lost in an exceedingly delicate, somewhat glistening 

 fibre, which enters and is lost in the substance of the cartilage. 

 It is easy to identify this branched mass of protoplasm as 

 being of the same nature as the cellular masses Avhich are 

 covered by the cartilage-substance, and to satisfy one's-self 

 that the process has been rendered visible, because the cavity 

 in which it is contained has been laid bare. 



This appearance is represented in Fig. 20, the depth of 

 shading in the drawing being, it is to be understood, intended 

 to make more prominent the contours of the different ele- 

 ments rather than to indicate the relative degree of difference 

 of their refractive properties. 



In sections so sealed up the substance of the cartilage can 

 sometimes be seen to be composed of parallel bands, having 

 approximatively the diameter of a human red blood-corpuscle. 

 The contour of these bands is well defined, resembling in 

 breadth and arrangement the similar bands that have been 

 described as being sometimes seen in silver preparations. The 

 size and arrangement of these bands are rendered in Fig. 

 15, which may be comj^ared with Fig. 14. In Fig. 15 

 the depth of shading is intended to enable the reader to 

 realise more easily the described arrangement. In the pre- 

 paration the contours are rendered visible only by slight 

 differences of refraction. 



In such prepai-ations these bands may be sometiines seen 



