520 THE THIRD HUXLEY LECTURE 



were able to struggle ; but this was effectually prevented in the following way : 

 The frog, wrapped in cold, wet lint, is held in the left hand, and the head, left 

 exposed for the purpose, is depressed with the forefinger so as to stretch the 

 ligament between the occiput and the first vertebra. The junction between 

 the brain and spinal cord is then divided with a tenotome, after which the 

 creature remains perfectly passive as long as may be desired. Comparatively 

 dull though we know sensibility to be in an animal so low in the scale as the 

 frog, it is a comfort to feel that this method must be attended with exceedingly 

 little pain. That caused by the division of the cord is probably almost as 

 momentary as the stroke of the tenotome ; and sensibility as well as motion 

 being abolished in the limbs, the creature cannot feel the tying of the naturally 

 sensitive toes or the subsequent dragging upon them. 



This arrangement had the further great advantage of allowing an irritant, 

 even in the form of a drop of liquid, to remain undisturbed at the particular 

 spot to which it was applied, instead of being diffused over the whole web by 

 the movements of the limb. Under these circumstances the highly interesting 

 fact was disclosed that, while the web generally was affected through the nervous 

 system with active congestion, that is to say, v/ith arterial dilatation and con- 

 sequent very free flow of blood, the characteristic stasis was limited to the area 

 on which the irritant acted directly. In spite of the widening of the tubes of 

 supply, the blood-corpuscles tended to lag more and more behind the liquor 

 sanguinis, till at length complete stagnation occurred. The obstacle to the 

 onward movement of the red discs seemed to be caused by adhesiveness on 

 their part. On careful examination, individual discs were sometimes seen 

 attached to the walls of the vessels. The white corpuscles also showed 

 a tendency to adhere to each other and to the vascular parietes ; and this was 

 seen in all degrees, from the disposition to trail along the venous radicles, 

 before referred to as occurring under slight irritation, to piling up of colourless 

 granular masses of leucocytes large enough to block a venous radicle.^ 



These appearances of the blood-corpuscles in the irritated area were such 

 as were seen in blood examined outside the body between two plates of glass. 

 I had observed similar granular masses of white corpuscles in blood from 

 my own finger, as well as individual leucocytes adhering to the surface of the 

 glass, along which, as has been since observed, they crawl by amoeboid move- 

 ments. 



In the red corpuscles the tendency to mutual adhesion shows itself in 



^ The accumulation of the white corpuscles in the vessels of an inflamed frog's web was described 

 in 1 84 1 by Dr. William Addison and Dr. C. J. B. WiUiams independently in the Medical Gazette of that 

 year. 



