KEPARATORY i:S'FLAM5IATI0N IN ARTERIES. 47 



111 concluding the discussion of tlie five series of experi- 

 ments above related, let us again call attention to the almost 

 unvarying uniformity throughout all of them, of apparently 

 one method of healing ; i. e., b}' means of the organization and 

 vancularization of the j)lO'Stic clot alone. 



Concerning the collateral circulation there is, as far as I 

 know, no dispute. Since the time of Porter it has been Avell 

 established that there are two species of collateral circulation, 

 a direct and an indirect, which, however, may both be present 

 in the same instance. 



Respecting the length of time required for the perfect estab- 

 lishment of the collateral circulation, the following observation 

 ma}' have some significance. 



A loop of intestine of a curarized frog was withdrawn 

 from the abdominal cavity and placed under the microscope, 

 so that the artery running along the inner curve of the gut was 

 in the field. Numerous small capillaries were observed to come 

 off from it and run around the intestine immediately beneath 

 the serous covering. These capillaries gave off numerous 

 branches which united with each other. The blood was now 

 interrupted in its wonted course through the artery hy press- 

 ing the point of a needle upon the latter, about half waj^ be- 

 tween the places of departure of two adjacent capillaries. 

 Immediatel}' the portion of the artery on the distal side of 

 the compressing needle became empty and contracted for a 

 little distance; at the same time the proximal end commenced 

 to dilate. Isochronous with this, the nearest capillary on the 

 proximal side began rapidly to dilate; in the space of a few 

 seconds the blood in it went by jerks, showing the arterial im- 

 pulse. A few seconds later the lateral anastomosing branches 

 also began to dilate rapidly. Later still, the first capillary 

 branching from the artery on the distal side of the point of 

 compression began to return its blood into the artery, at first 

 fclowly, then more rapidly, and finnlly with an arterial iinpnlse. 



