292 



PHYSIOLOGY 



CHAP. 



conditions, without special treatment, it speedily ceases to beat). By means 



of a cannula "tied to 

 the aorta, in the direc- 

 tion of the heart, he 

 caused blood or other 

 nutrient solutions to 

 circulate at a tempera- 

 ture of 38 C. under a 

 pressure corresponding 

 to the normal pressure 

 of the aorta. The fluid 

 keeps the semilunar 

 valves closed, circulat- 

 ing through the coron- 

 ary system of the heart, 

 and flowing out again 

 through the opening in 

 the right auricle. The 

 cardiac cavity remains 

 empty. A heart thus 

 artificially fed is cap- 

 able of continuing its 

 activity almost nor- 

 mally for many hours. 

 The graphic record of 

 its movements can be 

 taken by means of sus- 

 pension, or (after oc- 

 cluding the veins of 

 the right auricle) by a 

 manometer applied to 

 the pulmonary artery 

 (Siewert, 1904). 



FIG. 126. Engelmann's myograph for recording beats of frog's 

 heart in situ, when suspended from the apex by a thread 

 connected with a highly sensitive lever. The apparatus is a 

 two-armed lever, one arm of which is attached to a tine silk 

 thread, the other to a long straw or strip #f aluminium, which 

 magnifies the movements of the writing point on a smoked 

 surface. At the end of the thread is a fine glass hook, with 

 sharp point, which is inserted into the tip of the apex, after 

 cutting the fraenum by which the two layers of the pericardium 

 are united dorsally. 



II. The fact that 

 it impossible to keep 

 the isolated heart of different animals alive for a comparatively 

 long period has been used as the start- 

 ing-point for a series of researches on the 

 nutritive medium, or external chemical 

 conditions, necessary to its survival. 



This work has familiarised us with 

 the so-called physiological solutions, 

 which are artificial nutrient fluids, 

 capable (at least for a certain time) of 

 replacing the blood, since they contain a fc 

 all the elements necessary for sustaining FIG. i27.-cardiograms taken from 



., ..[, 0,1 i mi fr8 by Engelmanns method, a, 



the llle OI the heart. I he importance Commencement of ventricular 

 f\f fViia anKianf ovr>aarle fVo lirnifa rf ^-Vc systole ( Vs) ; b, commencement of 



ol tins subject exceeds the limits 01 uhe diastoieVd);c, curves of a tuning- 

 present chapter, for it may logically S n j hich vibrates 10 times per 

 be concluded that artificial fluids which 



are capable of sustaining the vitality of the excised heart will 

 also maintain the vitality of other organs or isolated tissues, or are, 



