and Laboratory Methods. '-'590 



as to compress the worm and prevent leakage from the cell. By twisting an 

 earthworm slightly when arranging it on the compressor one end maybe made to 

 give a dorsal, the other end a ventral, and intermediate parts a lateral view, so that 

 all anatomical details may be made out in one mount. The finest results are 

 obtained by selecting small earthworms having transparent body walls through 

 which the blood shows a pinkish color, and feeding them on moist clean filter 

 paper in a battery jar for a day or two to clear the intestine. 



To those who are not familiar with the results rapidly and easily attained in 

 the study of live earthworms by the combination of anesthesia by means of 

 chloretone with a compressor to flatten the animal slightly, the following sum- 

 mary will seem to be an exaggeration ; but it is a list of anatomical details distinctly 

 seen with the compound microscope in specimens mounted and studied by stu- 

 dents in the second year of the high school course. The structures made out 

 with such clearness as to be identified with certainty include the following: in 

 the body wall — the setae and their muscles, the longitudinal and circular muscles ; 

 in the coelom — the coelomic fluid and its corpuscles, the septa, and the parts of 

 the alimentary, circulatory, and nervous systems; in the alimentary system- — the 

 buccal sac, the pharynx, oesophagus, crop with its contents, gizzard with its con- 

 tained food and sand grains being moved around by the muscles seen in the 

 wall of the organ, the intestine exhibiting peristaltic motion and its covering of 

 chloragogue cells ; in the circulatory system — the pulsating dorsal vessel and 

 five pairs of "hearts," circular vessels, sub-intestinal, sub-neural and supra- 

 neural blood vessels, and the openings of vessels leading from the underside of 

 the dorsal vessel into the typhlosole ; in the nervous system — Ihe ganglia and 

 commissures of the ventral nerve chain, the pharyngeal collar and branch- 

 ing nerves, and the cerebral ganglia; the nephridial tubes are readily seen, the 

 funnels are more difficult, and the cilia in the mouth of the funnels are still more 

 difficult to see in action, but they have been seen clearly. While the above list 

 enumerates the details studied with a compound microscope in the hands of 

 young students, more than half the number have been studied also from the 

 screen both in class room and in public lectures. 



Directions for demonstrating three important phenomena of the circulatory 

 system : 



A. Circulation of the blood as seen in the capillaries. 



B. The pulsation of the auricles and ventricles of the heart. 



C. Valvular action in the heart and the movement of blood through it. 



All three of these phenomena cannot be shown in the same animal, or even 

 in different members of the same species; but each maybe demonstrated in 

 animals of two or more species. For the capillary circulation use the tail of a 

 fish or tadpole, or the web of a frog's foot ; for the pulsation of the auricles and 

 ventricles, several species of fresh water clams; and for a view of the moving 

 valves of the heart and the rapid inflow of blood, its sudden pause and equally 

 quick rush into the arteries, Daphiiia pulex and especially the nymphs of the 

 dragon-fly {Agrioii) may be used. 



A. The circulation of the blood in the capillaries is more easily demon- 

 strated in the tail of a tadpole than elsewhere for two reasons. First, the tad- 



