RHYTHMICAL CONTRACTIONS OF THE HEART. 55 



organ in a few moments resumes its normal function. We first notice a change from the 

 dusky hue it has assumed to a vivid red, which is owing to the circulation of arterial 

 blood in its capillaries. The distention then becomes gradually relieved, and, for a few 

 moments, the pulsations are abnormally frequent. If we now open an artery, it will be 

 found to contain red blood. An instrument applied to an artery will show a diminution 

 in arterial pressure and in the force of the heart's action, if the arrest of respiration have 

 been carried only far enough to moderately distend the heart ; or there is an increase 

 in the pressure and force of the heart, if its action have been nearly arrested. A few 

 moments of regular insufflation will cause the pulsations to resume their normal char- 

 acter and frequency. 



In the human subject, the effects of temporary or permanent arrest of respiration on 

 the heart are undoubtedly the same as those observed in experiments upon the warm- 

 blooded animals. In the same way, also, it is possible to restore the normal action of the 

 organ, if respiration be not too long suspended, by the regular introduction of fresh air 

 into the lungs. The numerous examples of animation restored by artificial respiration, in 

 drowning, etc., are evidence of this fact. In cases of asphyxia, those measures by which 

 artificial respiration is most effectually maintained have been found most efficient. 



Certain individuals have been said to have the power of temporarily arresting the 

 action of the heart by a voluntary suspension of respiration. The most remarkable case 

 of this kind on record is that of Colonel Townshend, which is quoted in many works on 

 physiology. Colonel Townshend was said to be able to arrest respiration and the action 

 of the heart so completely as to simulate death. When in this condition, the pulse was 

 not perceptible at the wrist or over the prascordia, a mirror held before the mouth was 

 not tarnished, and he was to all appearances dead. On one occasion, in the presence of 

 several medical gentlemen, he remained in this condition for half an hour ; afterward 

 the functions of respiration and circulation becoming gradually reestablished. This, to 

 say the least, is a very remarkable case, but it is credited by many physiologists. 



Cause of the Rhythmical Contractions of the Heart. 



The phenomena attending the action of the heart present few difficulties in their 

 investigation, compared with the study of the cause of the regular contractions and 

 relaxations, which commence early in foetal development to terminate only with life. 

 This interesting question has long engaged the attention of physiologists and has been 

 the subject of numerous experiments and speculations. It would be idle to follow the 

 various theories which have been proposed to account for this constant action, except as 

 a subject of purely historical interest ; for many of them are based upon a very imperfect 

 knowledge of the phenomena of the circulation. At the present day, although we are 

 perhaps as far as ever from a knowledge of the actual cause of the regular movements, 

 we are pretty well acquainted with the various conditions by which they are regulated 

 and modified. We know, for example, how to induce contraction in a living muscle or 

 one which is just separated from the organism and has not yet lost what we call its vital 

 properties, but we must confess our utter ignorance when we ask ourselves why it acts 

 in response to a stimulus. The advances that have been made in chemistry and micro- 

 scopical anatomy do not -disclose the so-called vital principle; and when we come to 

 examine the various conditions under which the heart will continue its contractions, we 

 are arrested by the impossibility of fathoming the mystery of the cause of contract ion. 

 The heart is, anatomically, very much like the voluntary muscles ; but it has a constant 

 function to perform and seems to act without any palpable excitation, while the latter, 

 which have an occasional function, act only under the influence of a natural stimulus, like 

 the nervous force, or under artificial irritation. The movements of the heart are not the 

 only examples of what seems to be spontaneous action. The ciliated epithelium is in mo- 

 tion from the beginning to the end of life, and will continue for a certain time, even after 

 the cells are detached from the organism. This motion cannot be explained, unless we 



