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AN AMERICAN TEXT-BOOK OF PHYSIOLOGY. 



connected with a manometer. This idea reappears in the Strassburg apparatus 

 described below. 



A valuable improvement was made by Kronecker, who invented a double 

 cannula, through one side of which the " nutrient " fluid enters the ventricle 



while it passes out through the other (Fig. 126). 

 The contents of the ventricle are thus contin- 

 ually renewed. In 1878, Roy l constructed the 

 instrument shown in Figure 127, by means of 

 which the changes in the volume of the heart at 

 each contraction are recorded on a moving cylin- 

 der. A great advance was made by Williams, 2 

 in the invention known as " Williams's valve," 

 which is the essential feature of the apparatus 

 devised by this investigator and others in 

 Schmiedeberg's laboratory at Strassburg. The 

 present form of this apparatus is illustrated in 

 Figure 128. A perfusion cannula is introduced 

 into the ventricle through the aorta. Through 

 one tube of the cannula the heart is fed from a 

 reservoir placed above it. Through the other 

 the heart pumps its contents into a higher reser- 

 voir or into the same reservoir. Thus the heart is " loaded " with a column 

 of liquid of known height and pumps against a measurable resistance. A 



FIG. 126. The perfusion cannula 

 of Kronecker. The ventricle is tied 

 on the cannula at d, a ring being 

 placed here to prevent the ligature 

 from slipping. The double tube, 

 shown in cross-section at e, divides 

 into the large branch a and the 

 small branch b. The nutrient solu- 

 tion enters the heart through 6 and 

 escapes through a. The silver wire 

 c can be connected with one pole of 

 a battery, the cannula serving as one 

 electrode, and the fluid surrounding 

 the heart as the other. 



FIG. 127 Roy's apparatus: the heart is tied on a 

 perfusion cannula and enclosed in a bell glass rest- 

 ing on a brass plate, 6, the centre of which presents 

 an opening covered by a rubber membrane. Vari- 

 ations in the volume of the heart cause the mem- 

 brane to rise and fall. The movements of the 

 membrane are recorded by a lever. 



FIG. 128. Williams's apparatus : H, frog's heart ; 

 V, V, Williams's valves ; MS, millimeter scale. The 

 apparatus is arranged to feed the heart from the 

 reservoir into which the heart is pumping. 



Williams's valve in the inflow tube prevents any flow except in the direction 



of the heart. A similar valve reversed in the outflow tube prevents any flow 



1 Koy, 1879, p. 453. 2 Williams, 1881, p. 3. 



