1920] on The Volume of the Blood and its Significance 47 



quantity must be returned by the veins, otherwise the blood would 

 soon all be accumulated in the peripheral parts of the body. Further. 

 the heart is capable of driving out the more blood the greater the 

 quantity it contains when contraction begins. This is what has been 

 called by Starling the " law of the heart." It depends on the fact 

 that muscular fibres contract the more powerfully the greater the 

 length to which they are stretched to begin with — within limits, of 

 course. 



We see, therefore, that the amount of blood driven through the 

 organs of the body in a given time depends on the amount present 

 in the heart at rest. Since this is a definite fraction of the whole 

 blood, the irrigation, as we may call it, of the body is in proportion 

 to the total quantity of blood available. The importance of sufficient 

 irrigation is obvious. The blood conveys to the active cells the 

 materials required for their work, and of these the most necessary is 

 oxygen. If the supply is too meagre, the first few cells with which 

 the blood meets exhaust it, and those beyond suffer from deprivation. 

 "Waste products are removed at the same time. 



Although the part played by the volume of the circulating blood 

 in relation to the capacity of the vascular system was realised by 

 Carl Ludwig and his school, who made many experimental investiga- 

 tions on the subject, the matter came especially into prominence in 

 connection with the explanation and treatment of the state known 

 as " surgical shock," but which occurred with alarming frequency in 

 men wounded in the late war. The name " wound-shock " is a more 

 comprehensive name, although the use of the word " shock " is liable 

 to give a misleading impression as to the rapidity of its onset, and 

 to cause confusion with " shell-shock," another unsatisfactory name, 

 but used to designate an affection of the nervous system of quite a 

 different nature from that brought about by the wounds themselves. 

 Wound-shock is not easily defined in such terms as to distinguish it 

 clearly from other similar states, such as that due to loss of blood, 

 but it may be said to be one of general collapse, ending in death 

 if not combated in some way. It does not come on immediately 

 after injury, but in the course of some two or three hours. It shows 

 itself by pallor, coldness, sweating, vomiting, thirst, low blood-pressure, 

 and the other symptoms which were early recognised as indicating 

 a defective circulation. 



But what is the actual cause of this collapse of the circulatory 

 mechanism ? It was soon realised, by those who examined cases of 

 wound-shock, that it was not due to any failure of the heart itself, 

 nor was the central nervous system involved, except indirectly in the 

 later stages. On the other hand, much difficulty was found in dis- 

 tinguishing between this state, even when attended by very little loss 

 of blood, and that resulting from great loss of blood unaccompanied 

 by serious injury. The latter is obviously the result of the defective 

 volume of blood and its consequences, since blood is known to have 



