240 



inflammation has been excited may be studied for hours with 

 the greatest ])recision. 



The amoeboid movements of white corpuscles, also the 

 changes of form of pigment cells, have, so far as I can judge, 

 their maximum activity in the fish. 



The parasites often met Avith are in themselves most curious 

 objects, especially " Gyrodactylus elegans," which was de- 

 scribed first in this journal (1861, p. 196). 



The common stickleback, when full grown, is perhaps the 

 best fish to use : the ti'ough described just fits it. Small 

 specimens of the gold fish may be used, if nothing more is 

 desired than a beautiful object. For physiological purposes, 

 fishes having little pigment, as the stickleback, 6cc., answer 

 best ; in addition, this fish is very hardy, and can always be 

 readily obtained. 



2. The Tadpole. — While losing its black pigment, and so 

 long as the tail remains, the tadpole presents a beautiful view 

 of the circulation, and of various tissues. Epithelium, nerve, 

 connective tissue, striped muscular fibre (the last often in the 

 act of contraction), are seen as they can nowhere else be seen. 

 The changes in inflamed parts are shown to perfection, in- 

 cluding phenomena of the greatest interest in relation to Pro- 

 fessor Cohnheim's theory. 



Ey putting the tadpole in warm water it may be kept 

 motionless for a short time, as is well known; this method is, 

 however, very unsatisfactory. 



By a modification of the trough described above, the tail of 

 the tadpole may be studied with the same ease as that of the 

 fish, though for shorter periods, on account of the deli- 

 cacy of organization of the tadpole. In consequence of the 

 greater thickness of the tail, moreover, 600 diameters is about 

 the limit of magnifying power practicable. 



The tadpole-trough shown in the sketch will be seen to 

 be on the same principle as that for the fish, aa is a similar 

 glass stage, raised ^ in. above the plate, and having beneath 

 it an aperture in the plate. B is a trough entirely covered in, 

 the cover of which (c) is here removed to show the interior. 

 The trough is kept constantly full of water by the supply- 

 pipe D ; E is the waste-pipe ; F is a little cage made of pieces 

 of pin wire, and of such a size as to hold easily the head of a 

 full-sized tadpole. 



The apparatus being placed on the stage of a microscope 

 inclined at an angle of 45°, a tadpole is deposited from a small 

 teaspoon on the lower part of the glass stage (about the 

 point g). 



The head immediately falls into the cage f, the tadpole 



