676 



SUMMARY OF CURKENT RESEARCHES RELATING TO 



been moistened witli water, is placed over the cylinder A, into which it 

 is then pushed with the rounded end of a glass rod, so that it takes up 

 the position represented in section by the dotted line. It is then 

 securely tied by a thread resting in the groove cut for the purpose at 

 the ujipcr edge of the cylinder. On now raising the pressure within 

 the chamber, by introducing air through the tube C, the membrane 

 bulges out in the manner indicated by the line x. When, however, it 

 is prevented from taking this position by the pressure of the glass 

 plate H, or rather by the web, or other part, which is placed below 

 the latter, it applies itself to this tissue, in the way represented by the 

 line D. 



The pressure of the air within the cylinder — that pressure to 

 which the tissue lying within the field of the Microscope is subjected — 

 is regulated by an arrangement which is illustrated by Fig. 158. The 



Fig. 158. 



caoutchouc bag A containing air, can be compressed between the brass 

 plates B, hinged together at one end, and which can be approxi- 

 mated by means of a screw. A T-tube connects the caoutchouc 

 bag on the one hand with a water manometer, and on the other (C) 

 with the cylinder A '(in Figs. 156 and 157). In this way the 

 pressure within the chamber can be regulated with the greatest 

 nicety. 



In the case of the web, care was at first taken that no part of 

 any of the toes was included within the area to be compressed. It 

 was afterwards found, however, that this precaution was unnecessary, 

 the result of raising the pressure applied being the same so long as 

 the part lying in the field was not too near one of the toes. 



