HEART. 



C09 



ing the frothy blood from the right side of the 

 heart. It is also necessary to remember this 

 circumstance in experimenting upon the .length 

 of time during which the heart remains con- 

 tractile after death, as the division or non-divi- 

 sion of the large veins at the root of the neck 

 in laying open the thorax may considerably 

 modify the results.* 



For the probable force exerted by the heart, 

 the share which the heart has in carrying on the 

 circulation, and the probable quantity of blood 

 expelled at each contraction, see the article 

 CIRCULATION. 



Frequency of the heart's action. The fre- 

 quency of the heart's action is considerably 

 modified by aee, condition of the other functions 

 of the body at the time, by mental emotions, and 

 by the original constitution of the individual. 

 Its movements are influenced by very slight 

 muscular exertion, and the extent of this appears 

 to vary at different times of the day. In the 

 foetus its movements are rapid, being about 

 140 in the minute. At birth it is from 130 to 

 140; at one year 115 to 130; second year 

 100 to 115; third 90 to 100; seventh 85 to 

 90; fourteenth 80 to 85; middle age 70 to 

 75; in very old age 50 to 65. The heart's 

 action generallysympathises powerfully with the 

 other organs of the body, and this has always 

 been regarded as a most important and necessary 

 guide in the detection and cure of diseases. 



It becomes strong and rapid in some cases of 

 inflammation, while in others it becomes rapid 

 and feeble. It becomes quicker after eating 

 and slower during sleep. It is much increased 

 in frequency during bodily exertion. In cases 

 of great general debility it becomes very quick 

 and feeble. It becomes more rapid and 

 weaker during inspiration, slower and stronger 

 during expiration. 



It is an important fact that when the con- 

 tractility of the heart is much enfeebled by 

 extensive injuries of the central organs of the 

 nervous system or of the other parts of the body, 

 (as when a limb is extensively crushed,) its 

 contractions are not only much weaker, but are 

 also greatly increased in frequency. It is also 

 worthy of remark that such injuries do not pro- 

 duce convulsive movements in this organ. The 

 effect which severe injuries and certain inflam- 

 matory affections have in greatly debilitating or 

 even destroying the contractility of the heart is 

 a fact of great practical importance, as it not 

 only explains the cause of the most alarming 

 symptoms in such cases, but also points out the 

 most appropriate remedies to avoid the chief 

 tendency to death. To this cause, for example, 

 we are to attribute the rapid and feeble pulse, 

 in concussion of the brain, in extensive mecha- 

 nical injuries, the shock after operations, exten- 



iburgh Medical and Surgical Journal, 1836. 

 performed these experiments, I was not 



* Edinbui 



When I performed these experiments 

 aware that I had been anticipated to a certain ex- 

 tent by Mr. Coleman. (Wilson on the Blood, &c. 

 p. 131 . ) It is very possible that the sinuses upon 

 the interior cava and hepatic veins in the seal may, 

 besides answering other purposes, have the effect 

 of preventing this mechanical distension of the 

 right side of the heart. 

 VOL. II. 



sive burns, peritonitis, &c. It is very fortunate 

 that the contractions of the heart become more 

 frequent when its contractility becomes en- 

 feebled. If the heart under these circumstances 

 had required, as we would a priori expect, the 

 presence of a greater quantity of blood to 

 stimulate it to contraction, instead of a smaller 

 quantity, as is actually the case, what would 

 have been the consequence ? It is evident 

 that since the resistance, under ordinary cir- 

 cumstances, which the heart has to overcome in 

 contracting, is, according to a well-known hy- 

 drostatic law, in proportion to the extent of the 

 area of the inner surface of the cavities of the 

 heart at the commencement of their contraction, 

 (each square inch of surface, according to the 

 experiments of Hales, having a pressure upon 

 it nearly equal to four pounds,) the more fre- 

 quent contractions, where there is a smaller 

 quantity of blood present in the heart at the 

 commencement of each contraction, will not 

 demand the same degree of muscular force for 

 their performance, as if these had been less 

 frequent. If, when the contractility of the 

 heart became debilitated, the presence of a 

 greater quantity of blood than usual in its 

 interior had been necessary to stimulate it to 

 contraction, and if the area of the inner surface 

 of the cavities of the heart be in proportion to 

 the quantity of blood contained there, it is 

 apparent that the movements of the heart would 

 have been much more rapidly and frequently 

 arrested when its contractility became enfeebled , 

 than they are under the actual arrangement. 



The influence of mental emotions upon the 

 movements of the heart requires no illustration, 

 for this is so universally experienced that in 

 common language the heart is considered to be 

 the seat of the affections and passions, and this 

 has had a powerful influence upon the phrase- 

 ology of all languages. 



In sanguine temperaments the heart gene- 

 rally contracts more frequently than in phlegmatic 

 temperaments. In women it is also generally 

 a little quicker than in men. 



It varies very much in different classes of 

 animals. 



Burdach* has given the following table col- 

 lected from numerous sources, as an approxi- 

 mative valuation of the frequency of the heart's 

 action in various animals. 



Number of pulsations in a minute.\ 



In the Shark . . 7 



Mussel 15 



Carp 20 



Eel 24 



Snake 34 



Horse 36 



Caterpillar 36 



Bullock 38 



* Physiologic, vol. iv. p. 251. 



t We cannot consider the number of pulsations 

 of the heart in a minute given in the above table 

 as by any means quite satisfactory. The number 

 of pulsations in the ox and horse is given on the 

 authority of Vetel in Froriep, Notizen, t. xxiv. p. 

 112. Other observers state the number of pulsa- 

 tions in a minute at from 38 to 52 in the horse, and 

 from 64 to 70 in the ox. 



2 S 



