HEART MUSCLE 157 



* (4) An absorbing organ. 



1 (5) It plays an important part in the 

 regulation of the temperature of the body.'* 



The illustration (Fig. 47) is taken from a 

 photo-micrograph showing an amplification of 

 100 diameters of the vertical section : the 

 focal distance was 50 inches ; and the objective 

 used was the j-inch. 



Heart Muscle (Human). 



The structure of the human heart is mar- 

 vellous in every microscopic detail. It must 

 be so in order to do the incessant and 

 gigantic work it does. Throughout life it 

 never ceases for rest, day or night. It is a 

 wonderful and startling thought that for 60, 70, 

 or even 100 years it continues its rhythmical 

 beats, pumping the vital fluid through the 

 complex human system of arteries, capillaries, 

 and veins. If it were to take a single half- 

 hour's rest we should die. 



* Kirkes, Handbook of Physiology. Morrant Baker's 

 Edition. (John Murray.) 



