674 



SUMIIARY OF CUREENT RESEARCHES RELATING TO 



breatlie. A clip shown at the end of the box can be screwed down by 

 the nulled head, more or less, so as to confine the frog's leg (which is 



Fig. 155. 



brought through the large hole shown in the box), the web of the foot 

 being placed over the aperture of the plate, and examined in the 

 usual way. 



Apparatus for Investigating Capillary Blood-pressure (in the 

 Frog's Foot).* — Drs. C. S. Eoy and J. Graham-Brown describe the 

 apparatus they employed in their .investigations on this subject. 

 Their observations were confined to tissues, the capillary circulation 

 of which could be watched through the Microscope, the web of the 

 frog being preferred, since it permits a study of the phenomena of the 

 blood-flow through the minute vessels without interfering to any im- 

 portant extent with either the general or local circulation. To con- 

 trol the data obtained, however, most of the experiments were repeated 

 on the tongue and mesentery of the frog, and on the tails of newts and 

 small fishes. The principal facts learned were of such a nature as to 

 leave little doubt of their general applicability to the peripheral circu- 

 lation of warm-blooded animals. 



In Fig. 156 is represented (somewhat diagrammatically) one of the 

 arrangements which was finally found the most convenient. In the 

 centre of a brass plate, measuring 10 cm. by 4*5 cm., is screwed the 

 cylinder A (2*8 mm. internal diameter, and its upper edge 6 mm. 

 above the plate), closed below by the glass plate B, the junction being 

 air-tight. The upper outlet of the cylinder is closed by the delicate 

 transparent membrane D, which jiresses upon the web, tongue, or 

 other part examined, when the pressure of the air within the cylinder 

 is raised. Counter-pressure is exerted by the thin glass plate H, 

 which is so arranged that it can be fixed at any desired height above 



* Journ. Physiol. (Foster^ ii. (1880) pp. 325-30. 



