2274 Journal of Applied Microscopy 



The Technique of Biological Projection and Anesthesia of 



Animals. 



Copyrighted. 



XIII. THE ANESTHESIA OF ANIMALS.— Continued. 



Nymph of Drag'Vi- fly. — These nymphs are usually found in considerable 

 numbers, during fall and spring collecting trips, on submerged wood and plants. 

 They are readily kept alive in batter-jar aquaria, but must be removed from 

 aquaria in which hydras are to be kept, as they eat the latter. The points of 

 special interest which they present to the student include the trachea; and tracheal 

 gills, the brain and its relation to the eyes, and the heart which displays valvu- 

 lar action with unusual clearness. The heart is in the next to the last somite of 

 the abdomen, between the right and left tracheal trunks. Its largest valves are 

 close to the posterior end, are set in the vertical plane, usually work at a com- 

 paratively slow rate, and display valvular action clearly under a low power 

 objective. 



As the nymphs differ greatly in color and transparency, the lightest colored 

 specimens should be selected for studies of their anatomy. Place the nymph in 

 a mixture of equal parts of water and one per cent, chloretone solution. If this 

 strength does not soon bring on a state of anesthesia, add more chloretone, or, 

 in case the specimen is very resistant to its action, place it in full strength 

 chloretone solution. The specimen from which the accompanying illustrations 

 were made, lived for about an hour in a small cell filled with the full strength 

 solution. 



The accompanying engravings, Figs. 7 and 8, pages 2224 and 2225, taken 

 from photographs of a live nymph as projected on a screen for class study, show 

 the distribution of the more important tracheal trunks which are seen as dark 

 lines in the head, prothorax, terminal segments of the abdomen and tracheal gills. 

 Extending across the head between the eyes is the brain, in which the tracheae 

 are narrow and dendritic. The eyes, which were easily seen to be compound in 

 the large view on the screen, receive special trachere. While tracheal gills are 

 not unusual, this species shows clearly their connection with the main tracheal 

 trunks of the abdomen and their fine terminal branches in the plate-like gills. 



Branchipus. — -The absence of a carapace renders these animals so transpar- 

 ent that their anatomical structure, the peristalsis of the intestine, pulsation of 

 the heart, and flow of the blood are easily studied in anesthetized specimens. 

 The rate of movement of the phyllopods may be perfectly controlled by the use 

 of chloretone, and, in weak solutions of the drug, the animal's curious normal 

 mode of swimming with the phyllopods up is reversed and the dorsal side 

 assumes its usual position, as seen in most species of animals. 



To study the effect of weak solutions on their swimming, place specimens of 

 branchipus in water sixteen to twenty parts with one part one per cent, chlore- 

 tone. For study under dissecting or compound microscope in the anesthetized 

 state, place them in a watch glass with the same strength of solution named 



