92 LABORATORY MANUAL OF GENERAL PHYSIOLOGY 



dog. Turn the handle and observe the arterial pressure (right Hg manom- 

 eter) and the venous pressure (left Hg manometer). Feel the pulse in 

 the arterial tube (at right). 



Now connect the side tube (to right of bamboo resistance) to a mem- 

 brane manometer. Clamp off artorial manometer. Record pulse tracing 

 on a kymograph drum with signal magnet, marking time in seconds. The 

 record is identical with the pulse of the carotid artery of the dog (cf. 

 Porter, Science, 21: 752, 1905). 



XIV. INVERTEBRATE HEARTS 



ANNELID HEART 



The worms are the lowest class of animals in which any structure 

 analogous to the heart is found. In the earthworm the circulation is 

 closed and maintained by peristalic waves of the dorsal vessel (and con- 

 traction of aortic loops). 



1. Direction of Wave in Heart of Earthworm. — Pin a worm (dorsal side 

 up) in a dissecting pan. Observe the dorsal vessel through the skin along 

 median dorsal line. Any correlation with peristallic wave in body 

 muscles? At which end of the dorsal vessel does the wave start? Place a 

 mm. rule beside the animal and determine the rate of conduction at 5°, 10° 

 and25°C. (Cover with water at desired temperature.) If the worm is cut 

 in 3 pieces, does the direction change? (cf. Clark, "Comp. Physiol, of 

 Heart," pp. 3-4). 



2. Circulation in the Leech. — Curarize (inject 0.2 cc. 1% curare half hr. 

 before experiment) a medicinal leech (this paralizes the body muscles but 

 does not affect the vascular contractions). Avoid injecting alimentary 

 canal. Each longitudinal vessel consists of a thin walled tube lying 

 laterally in the body cavity, slightly to the ventral side. Immerse animal 

 in Ringer's solution diluted to j^. Cut through lateral body wall just 

 deep enough to pass through longitudinal muscles (cut through ventral 

 edge of the yellow line present in some species). The vessel is now exposed 

 along the whole length of the excision (bulging around the distended 

 nephridial vesicles). Determine the rate and sequence on each side (cf. 

 Gaskell, Trans. Roy. Soc, 205: 168, 1914). Text p. 435. 



ACCESSORY HEARTS IN INSECTS 



Insects have a feebly developed open circulatory system since oxygen 

 is transported by the tracheae. The accessory leg hearts appear to be 

 myogenic unlike the lymph hearts of the frog. 



3. Leg Heart in Notonecta. — Place the insect dorsum down in a dry- 

 watch glass. Under the microscope observe the pulsating organ in the 

 femorotibial joint (just below knee) of the swimming leg (during moments 



