BY DR. KLEIN. 31 



ration for a sufficient length of time, the observer is sure to see 

 many corpuscles in which the3 T lie, some partly, some'entirc-lv 

 outside of the outline of the pale disk. The latter (again fol- 

 lowing Briicke) we designate cecoid. Briicke teaches that the 

 zooid consists of the nucleus and the haemoglobin ; that it with- 

 draws from the cecoid which it previously, as it were, inhab- 

 ited, and collects itself around the nucleus, so as to form an 

 independent individual, capable of a separate existence. In 

 describing furlher on similar appearances observed during the 

 action of carbonic acid gas, we shall suggest another explana- 

 tion of the phenomenon. 



Action of Tannin on Human Blood Roberts's Re- 

 action. The action of tannin on the colored corpuscles of 

 human blood resembles that of boracic acid on newt's blood. 

 When two per cent, solution of tannin is added to human 

 blood, the corpuscles, which have been already rendered star- 

 shaped by salt solution, acquire an even contour. Soon after, 

 a sharply-defined, 3 r ellowish-green, roundish body is seen, either 

 just within or at the margin of each corpuscle, or even out- 

 side of it, while the corpuscle itself has become colorless. 



Action of Gases on the Blood. For the study of the 

 action of oxygen and carbonic acid gas on the blood corpus- 

 cles, either of the movable stages represented in Figs. 2, 3, 

 and 16 may be used. Around the edge of the central chamber 

 we form an annular wall of putty. We then make on a cover- 

 glass a preparation of newt's blood, to which about half its 

 volume of distilled water has been added. The glass is then 

 inverted over the chamber (upon the floor of which a drop of 

 water has previously been placed) with the preparation down- 

 wards, so "that its entire periphery presses evenly upon the 

 putty ring. The chamber is thus converted into an air-tight 

 cavity. In Fig. 3, two tubes (H, I), with India-rubber con- 

 nectors fitted to them, are shown, both of which communicate 

 with the chamber in such a way that when it is closed above 

 and below, a stream of gas passing in by the one escapes by 

 the other. By means of an apparatus in communication with 

 the tube H, the construction of which will be readily under- 

 stood from Fig. 5, the observer is able to fill the chamber at 

 will with carbonic acid gas or with air. This is accomplished 

 as follows: 



If the bottle containing hydrochloric acid is raised, the clip 

 n opened, and the India-rubber tube a shut between the teeth, 

 the carbonic acid, which is developed in M, after it has passed 

 through the wash-bottle V, flows into the chamber, and is dis- 

 charged l>y the tube b. By proceeding in this manner one 

 hand is left free, and can be used for adjustment. To inter- 

 rupt the current of gas, all that is necessary is to close X and 



