1042 



RECORD OF CURRENT RESEARCHES RELATING TO 



Fig. 113. 



etherized * without affecting the circulation, and may then be placed 

 on the frog-plate, shown in Fig. 113, in an erect position, with its feet 



on the circular glass, a little 

 soft tape being placed — not too 

 tightly — round the body to keep 

 it erect. The web of the foot 

 may now be moistened with a 

 little cold water, and the plate 

 laid on the stage for examina- 

 tion. 



If sufficiently etherized, the 

 frog will remain perfectly quiet 

 for half an hour, and both feet 

 may be examined alternately. 

 The toes must of course be 

 spread out so as to stretch the 

 web, which should be moistened 

 occasionally with a camel-hair 

 pencil dipped in cold water. 

 The process may be repeated 

 many times on the same frog 

 if carefully managed, but after 

 each examination it should be 

 piit into a vessel with a little 

 cold water, till it recovers con- 

 sciousness. 



Sternberg's Culture-cell.f — There are many experiments in 

 which a culture-cell is required which will preserve the blood in a 

 fluid condition, free from atmospheric contamination, and yet sur- 

 rounded by a sufficient amount of air to furnish the necessary oxygen 

 to organisms that may develop from any germs that may be present 

 in the blood. In addition to this it is necessary that a very thin 

 stratum of blood should be within reach for examination by the 

 highest-power immersion objectives. 



The Boldeman cell fulfils the first requirement. A central emi- 

 nence is surrounded by a circular channel, ground in the glass, which 

 serves the purpose of an air-chamber. The summit of the central 

 eminence is slightly concave, and the drop of fluid to be observed is 

 placed upon this and protected with a thin glass cover, which is 

 attached to the slide by a circle of cement, or simply by a little oil. 



The main objection to this cell was found by Mr. G. M. Sternberg, 

 Surgeon U.S. Army, to be that the stratum of blood held in the 

 shallow cup of the central eminence was too thick for satisfactory 

 examination with high powers; that portion of the fluid next the 

 cover, which could be brought into focus, being shut off from the 



* It may always be known when the frog is fully under the influence of the 

 ether, by placing it on its back, before taking it out of the bottle, as it will not 

 remain quietly in this position except when etherized. 



t ' Am. Mon. Micr. Journ.,' i. (1880) pp. 141-3. 1 fig. 



