ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 



647 



Banvier's * (fig. 113) consists of a glass vessel filled with quicksilver 

 which can be raised and lowered on a retort-stand. The rise of the 

 quicksilver in the intermediate vessel compresses the air which it 

 contains as well as that in the bottle containing the injecting fluid, 

 which is forced out as in the previous case. In another form (fig. 114) 



Fig. 114. 



Fig. 115. 



the pressure is obtained by compression of an indiarubber ball K 

 communicating with an air-reservoir E (M being a manometer). 



Hering's f (fig- 115) consists essentially of two glass bulbs, A A', 

 having a thin glass tube pass- 

 ing through the stoppers in 

 their necks, and by which the 

 bulbs communicate with each 

 other. A flexible tube from 

 each bulb passes into one or 

 other of the bottles E E, con- 

 taining the injecting fluid. 

 The ends of the glass tubes 

 are drawn out so fine that the 

 quicksilvei- passes only a drop 

 at a time from one to the other 

 (even when the air is com- 

 pressed). When the bulbs are 

 turned on their axis, and in- 

 stead of the horizontal posi- 

 tion I., take the oblique one II., the quicksilver will flow from A to 

 A', and compress the air in the bulb A', and act upon the injecting 

 fluid in the vessel E. The nearer a vertical position is approached, 

 the greater the pressure will be by which the injecting fluid is forced 

 into the blood-vessels. The two bottles, E and E, are alternately 

 used according as one or the other of the bulbs is uppermost.j 



* Thanhoffer's 'Das Mikroekop und seine Anwenduns;,' 1880, pp. 189-90 

 187-8 (2 figs.). 



t Ibid., pp. 103-4 (1 fig.). 



X The figure, which is a cliche of the original, should have indicated one of 

 the two positions of the bulbs by dotted lines. As drawn, there appear to be four 

 bulbs. B, C, and D are not (txiiiiuried but their function in obvious. 



