THE STRUGGLE FOR LIFE. 213 
bition by Moses, was most probably dictated, not by any 
idea that there was anything sacred about the blood, or 
that it partakes in an exceptional manner of the essence of 
life. The more probable reason is, that the blood is an 
easily putrescible body, and its consumption, especially in 
hot climates, would have caused disease. It was part of 
the wonderful sanitary code promulgated by Moses, which 
is, in some respects, even in advance of modern regulations. 
Moses made his Sanitary Bye-laws part of the religion of 
the Israelites, and to their observance, was doubtless due, 
in a great measure, their preservation during trying circum- 
stances, and also their eventual predominance among the 
insanitary Orientals among whom they lived. And who 
shall say that the continued existence of the Jews as a 
peculiar race, never absorbed by any of the nations among 
whom they dwell, is not due, to some extent, to their con- 
tinued observance of the Mosaic law? At all events it is 
a well known fact, that the Jews rarely suffer from some 
of the diseases common among their neighbours. 
As both the continued life, and also the due performance 
of the functions of every cell of the body, depend on the 
free access to it of the nutrient fluid, that is the blood, I 
will now give a short sketch of the manner in which the 
blood circulates through the body. 
If an animal be opened after death, there will be found 
in its body a number of tubes, some of these have thick 
walls, are empty, and are called Arteries, while others have 
thinner walls, contain blood, and are called Veins. Tracing 
these tubes in one direction, they will all be found to end 
in the heart, while in the other they keep on giving off 
branches, until they become so small as to be invisible to 
the naked eye. After death, one side of the heart and the 
arteries are found to contain air, whence the name. The 
other side of the heart and the veins contain blood. Thus 
much has probably been known, since primeval man first 
