Studies on the conditions of activity in endocrine glands. XVII, A lasting preparation of the denervated heart for detecting internal secretion, with evidence for accessory accelerator fibers from the thoracic sympathetic chain / by W.B. Cannon [and others].

Date:
[1926?]
Catalogue details

Licence: Public Domain Mark

Credit: Studies on the conditions of activity in endocrine glands. XVII, A lasting preparation of the denervated heart for detecting internal secretion, with evidence for accessory accelerator fibers from the thoracic sympathetic chain / by W.B. Cannon [and others]. Source: Wellcome Collection.

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    tions so that animals thereafter could be kept alive for a considerable period and in normal health, for study of conditions influencing the rate of beat. It appears that the only investigator who has hitherto reported having made such a preparation for the study of cardiac function is Friedenthal (1902). He destroyed the middle and lower roots of the left vago-acces- sory nerves at the medulla, and severed the right vagus below the recur- rent branch. Then he removed the lower cervical.and upper thoracic ganglia of the sympathetic chain. One dog and several rabbits survived the operation and were observed. The main features emphasized in the report on the dog were that the resting pulse was little changed from the normal, that the cardiac nerves are not essential for existence (the animal lived 8 months after the isolation was completed), and that capacity for muscular work (i.e., running) was much reduced. Unfortunately Frieden- thal did not record the pulse. His statement that the rate of the dener- vated heart can still be markedly influenced by changes of blood pressure (which is incorrect (see Cannon and Rapport, 1921)) might indicate that the rate was not steady. As will be shown later, the conditions governing the heart are much more complicated than he realized, and the only proof of isolation from the central nervous system is relative indifference to disturbing conditions after humoral factors have been excluded. Frieden- thal should have studied carefully the heart rate under different circum- stances. This he apparently did not do. In our experiments we have made use of the cat. The innervation of the heart in the cat. The scattered distribution of nerves near the heart renders practically impossible any satisfactory denervation of the organ by operating in that region. It is necessary to find a place where the relations are simpler. At first we thought we might open the pericardium and by cutting and applying phenol we might de- stroy the nerves as they course along the vessels which connect the base of the heart with the pericardial wall. Our attempts were only partially successful, however, and we therefore turned elsewhere. The other situa- ation in which the relations are relatively simple is at the origin of the cardiac nerves—the vagus trunks and the stellate ganglia. The chief difficulty with any simple exclusion of vagal influences, as by section of the nerves in the neck, lies in the consequent serious disturbances of respira- tion and digestion. To avoid these troubles one recurrent laryngeal nerve must be preserved in order that the larynx may act properly and pro- tectively, and one vagus trunk must pass to the abdomen in order that the digestive functions may continue normal. Some preliminary experiments showed that it is possible to exclude the influence of the right vagus by cutting strands which reach out from it towards the heart near the mouth of the superior vena cava and the
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