March 4, 1920] 



NATURE 



The amount present in each part, including the 

 heart itself, is obviously in proportion to the 

 capacity of each part. 



The heart, however, works as a pump. The 

 way in which the blood is circulated was first 

 clearly propounded by Harvey in 161 6, although 

 Leonardo da X'inci came very near to the dis- 

 covery more than a century before. Harvey saw 

 the blood sent out from the heart, propelled to the 

 tissues in the arteries, and returned to the heart 

 by the veins. The course of the blood from one 

 to the other through the minute capillaries could 

 not be seen until the invention of the microscope 

 by Leeuwenhoek, who made use of it in 1686 to 

 observe the blood traversing the capillaries in the 

 tail of the tadpole. 



I The heart, then, when it contracts, drives out 

 the blood which is contained in its cavities, or 

 nearly the whole of it. This same 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 Ludw»g 

 and his school, who made many experimental 

 investigations on the subject, the matter came 

 especially into prominence in connection with the 

 explanation and treatment of the state known 

 previously 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 im- 

 pression as to the rapidity of its onset, and to 

 cause confusion with "shell-shock," another un- 

 satisfactory name, but used to designate an affec- 

 tion of the nervous system of quite a different 

 nature from that brought about bv the wounds 

 Bi themselves. Wound-shock is not easily defined in 

 V such terms as to distinguish it clearly from other 

 B similar states, such as that due to loss of blood, 

 B but it may be said to be one of general collapse, 

 ■ ending in death if not combated in some way. 

 K NO. 2627, VOL. 105] 



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, vomit- 

 ing, thirst, low blood-pressure, and the other 

 symptoms which were early recognised as indi- 

 cating a defective circulation. 



But what is the actual cause of this collapse 

 of the circulatory mechanism? It was soon real- 

 ised, 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 

 distinguishing 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 left 

 the body. But why do the former cases also 

 appear to be suffering from the same condition, 

 when scarcely any blood has actually been lost? 



In the endeavour to find an explanation for this, 

 we may call to mind the circumstance that blood 

 may be effectively removed from cLrculabion 

 by being pooled away in some part or, other 

 of the vascular system, as, for example, l)y 

 a great dilatation of this part. The amount 

 which is available for propulsion by the heart 

 to serve for continuous irrigation of the 

 tissues is reduced as much as it would be 

 if the blood held in the pool were actually lost 

 to the outside. Such changes in the capacity of 

 the peripheral blood-vessels play a large part in 

 the regulation of the blood-pressure and the 

 supply of blood to various organs. We may 

 inquire whether anything of this kind happens 

 after severe injuries. 



The first step taken in the course of this inquiry 

 was the discovery that some poisonous substance 

 is produced in injured tissues. This, passing into 

 the blood, is carried to all parts of the body. Sir 

 Cuthbert Wallace, some years ago, had noticed 

 that operations in which the cutting of large 

 masses of tissue was involved were especially 

 liable to be followed by shock. Qu6nu and others, 

 during the war, were struck by the rapid benefit 

 frequentlv ensuing from removal of the injured 

 parts or even when they are tied off from con- 

 nection with the rest of the blood-vessels, if such 

 is possible. Cannon and myself found that we 

 could produce the state of wound-shock in anaes- 

 thetised animals in the laboratory, and that it was 

 due to a chemical agent, not to anv effect on 

 nerves. This being so, we see that we can replace 

 the name of " wound-shock " by the more descrip- 

 tive one of "traumatic toxaemia." 



But can we form any conclusion as to the 

 chemical nature of this toxic substance or as to 

 the way in which it acts? It is evidently pro- 

 duced too quickly to be a result of bacterial infec- 

 tion, and, indeed, McNee was able to exclude this 

 possibility quite definitely. Dale and Laidlaw, 

 however, showed that there is a compound of 

 known chemical structure, called "histamine," 



