THE SYSTOLIC OUTPUT OF THE HEART 



49 



second in a dog was found to be '00157 of the body weight (25 

 kilos.). 



Obtained by such different methods, Zuntz and Tigerstedt's results 

 roughly agree. Thus the output per second was — 



•00085 of body weight (maximal "00132) Kabbit Tigerstedt. 



•00122 ...... Horse Zuntz. 



•00157 ...... Dog Zuntz. 



Stewart has recently estimated the output by a new method. 1 A definite 

 amount of 1*5 per cent, solution of NaCl is injected into the right auricle 

 through the jugular vein at a uniform rate. From the femoral artery samples 

 of blood are collected (1) just before, (2) during the injection. The quantity 

 of 1*5 per cent. NaCl solution necessary to add to sample 1, to make its 

 NaCl content equal to that of sample 2, is determined. This determination 

 yields the amount by which the injection is diluted with blood in the heart. 

 If the quantity of the injection in a given time be known, and the extent of 

 its dilution, it is obvious that the output of the heart can be calculated for that 

 time. Stewart's results agree closely with those of Zuntz. 



From these data the systolic output in man can be calculated to be 

 a little more than 100 c.c. By the use of hydrodynaniical formulae the 

 output was reckoned to be 

 160 c.c. (see p. 43), but this, 

 as already stated, is probably 

 much too high. 



Such methods of investiga- 

 tion as the above are unsuit- 

 able for prolonged researches 

 on the output of the heart 

 under the varying conditions 

 of experiment. An attempt 

 has therefore been made to 

 use the pericardial sac as the 

 chamber of a plethysmograph, 

 and thus obtain records of the 

 changes of cardiac volume. 

 The pericardial wall is not, 

 however, sufficiently rigid for 

 the purpose ; moreover, the 

 diastole of the heart is 

 impeded whenever this sac is 

 distended with fluid. The ex- 

 perimental difficulties in the 

 way of inquiry have been 

 recently solved by Eoy and 

 Adami's invention of the 

 cardiometer. 2 



Cardiometer. — Roy and Adaini. 



The cardiometer consists of a metal box, constructed in two parts, these are 

 united by a hinge joint. After the thorax has been opened, and the peri- 

 cardium slit open, the heart is slipped within the opened cardiometer, and this 

 is then closed. The vessels issue from the heart through an orifice in the 

 cardiometer, and to the edge of this opening the parietal layer of the peri- 



1 Journ. Phi/siol., Cambridge and London, 1897, vol. xxii. p. 159. 

 "Phil. Trans., London, 1892, vol. clxxxiii. B, p. 202. 



VOL. II. — 4 



