296 



PHYSIOLOGY 



3. The phenomena of arterio- 

 sclerosis hardly ever appear before 

 adult age, and frequently seem to be 

 the result of natural causes, since grave 

 irregularities of function or habits are 

 by no, means always noticeable in old 

 people attacked by it. 



Cazalis's aphorism, " On a 1'age de 

 ses arteres," is based on the clinical 

 observation that arterial changes 

 exercise a powerful influence on the 

 whole system. Boerhaave, who re- 

 garded the whole body as consisting of 

 vessels and fibres, believed, as Haller 

 points out, that senile decay and death 

 are due to the hardening of the arteries, 

 " ut cor earn resistentiam superare 

 nequeat." Although it may be an 

 exaggeration to ascribe as does 

 Demange all the changes which take 

 place in old age to this cause alone, its 

 great importance in the acceleration 

 of the other phenomena of senile 

 decay cannot be denied. 



Metschnikoff agrees that arterio- 

 sclerosis is one of the main causes of 

 senile decay ; he however ascribes no 

 physiological significance to it, but con- 

 siders it to be invariably due to chronic 

 intoxication, which may be caused by 



FIG. 122. Reproduction of a drawing by Leonardo da 

 Vinci in the Accademia di Belle Arti at Venice. (The 

 general divisions are partly taken from Vitruvius.) 



The height of the man of average stature is eight 

 head lengths, as is seen in the drawing. The half of the 

 body length is at the end of the pubis. If the arms be 

 raised horizontally, the distance between the tips of 

 the right and left middle fingers is equal to the entire 

 height of the man. If the legs be stretched out and 

 the arms raised to the level of the top of the head, as 

 shown in the sketch, the navel becomes the centre of 

 a circle which passes through the extremities of the 

 outstretched limbs, and the space between the feet 

 and the pubis forms an equilateral triangle. 



From above the breast to the top of the head is a sixth 

 of the whole figure. From the line of the nipples to the 

 top of the head, from the nipple line to the pubis, from 

 the pubis to below the knee, and from this point to 

 the sole of the foot, are four equal spaces, each measur- 

 ing two head lengths, or a quarter of the man ; just as 

 we have the same length from the tip of the middle 

 finger to the end of the biceps as at the widest point of 

 the shoulders. From the elbow to the shoulder is one 

 head or four nose lengths. From the centre of the eye 

 to the navel and thence to the beginning of the knee- 

 cap are spaces of equal length. (This explanation of 

 the figure is by Leonardo.) 



