i 220 



HANDBOOK OF PHYSIOLOG1 



CIRCULATION - II 



O 



Control Stott 



Subj JM.J5WM 

 Tr*nchfool 



2RT J 



_ IO T IOO en 



S olo t 



E 



I 



= 4RT 



° 10 _ 100 



«W ^ am) 



FIG. 2. Rheoplethysmographic recordings showing the simultaneous curves of volumes and rates 

 of digital inflow, outflow, and the difference between inflow and outflow for the tip of the right 

 second toe (2RT) during a single pulse cycle. A represents the curves for the subject resting supine 

 in a comfortable environmental atmosphere, B following heating of the trunk, and C following pro- 

 caine block of the posterior tibial nerve. Iy and I K represent the time courses of the volume and rate, 

 respectively, of inflow; Oy and Or, volume and rate, respectively, of outflow ; Dy and D R difference 

 between the volume and rate, respectively, of inflow and outflow. The reader should refer to the 

 iterature (10, 11) for a discussion of rheoplethysmography. See following pages for 2/? and iC. 



degree to blood in die cutaneous capillaries. When 

 the velocity of blood is slow, more oxygen is removed 

 by the tissues, the concentration of reduced hemo- 

 globin increases, and the color of the skin darkens 

 and becomes bluer. 



The integration of skin color and temperature 

 has been aptly stated by Lewis (49). These charac- 

 teristics, of considerable physiologic and clinical 

 significance, are: 



"Warm pale skin: This is a skin through which 

 blood flows rapidly for many minutes. It is warm 

 because flow is fast, pink because of the abundant 

 supply of fully oxygenated blood, and pale because 

 the skin is well nourished and minute vessel tone is 

 therefore high. 



"Warm deeply coloured red skin: Such skin has been 

 irritated, by heat or otherwise, it is in a state of 



inflammation, or it is skin in which arterial vasodila- 

 tation has recently been brought about through 

 nervous channels or by means of drugs such as 

 amyl nitrite. 



"Cold pale cyanosed skin: This is skin to which the 

 blood-flow is very slow or absent. If the tint of the 

 cold skin is violaceous or if the skin is blanched, the 

 circulation to it is absent and has been arrested in it 

 for many minutes. Minor grades of cyanosis are, as 

 previously stated, of much less significance. 



"Cold deeply coloured cyanosed skin: This is skin in 

 which the circulation is very slow, and in which 

 blood-flow has been failing for a long time or in 

 which there is a process of low-grade inflammation. 



"Cold deeply coloured red skin: If skin is sufficiently 

 cold, 10° C (50° F) or less, the blood will not part 

 with its oxygen, but the minute vessels are damaged 



