ARTICLES 277 



especially to muscle, whether by shell wounds or by surgical 

 operations, observations made at the casualty clearing stations 

 in the late war showed that a state of the circulation similar to 

 that produced by histamine was present. The obvious con- 

 nexion between severe shock and massive injury suggested 

 experimental test. Col. Cannon, of Harvard University, and 

 the present writer found that injury of the thigh muscles in 

 anaesthetised cats and dogs brought on a condition like that 

 of wound shock, and we were able to show that it was not due 

 to irritation of nerves, but to the passage into the blood of 

 some chemical product of the injured tissue. The fact that 

 the state, whether accompanied by haemorrhage or not, owes 

 its dangerous character to the want of blood in circulation, 

 pointed to the treatment which alone was found successful — 

 namely, the filling up of the circulation by transfusion of blood 

 or of some appropriate artificial solution, such as gum arabic 

 in saline. 



In regard to the nervous supply of the capillaries, some 

 recent observations by Krogh are of importance. He shows 

 that it is possible, by touching with a glass needle over the 

 situation of a closed capillary in the frog's tongue, to make 

 this vessel dilate, and that the extent to which the dilatation 

 spreads depends on the strength of the stimulus. A similar 

 local effect can be obtained on an arteriole. Degeneration 

 of the nerves to the tongue or the application of cocaine very 

 nearly abolishes the effect, and what remains is sharply localised 

 to the point stimulated. The conclusion is drawn that the 

 spreading of the effect is due to an axon-reflex in sensory 

 fibres, analogous to that suggested by myself (1901, p. 196) 

 for the case of the vaso-dilatation produced by stimulation of 

 the peripheral ends of sensory nerve fibres. 



There remains for brief discussion another aspect of the 

 capillary circulation which has important physiological and 

 pathological relations. In the shock produced by histamine, 

 and also in that of wounds in man, it was found that not only 

 was the blood in effective circulation diminished, but what 

 was in circulation had become more or less concentrated by 

 loss of plasma. To understand the cause of this phenomenon, 

 we must consider the evidence as to the permeability of the 

 capillary wall. It is a familiar fact that, when blood is lost, 

 fluid is taken up from that in tissue spaces in order to restore 



