TRANSFUSION OF BLOOD. 1 45 



It consists of a long cylindrical glass-vessel, G, suited to accommodate a limb. The opening 

 through which the limb is introduced is closed with caoutchouc, and the vessel is filled with 

 water. There is an opening in the side of the vessel in which a manometer tube, filled to a 

 certain height with water, is fixed. As the arm is enlarged owing to the increased supply of 

 arterial blood passing into it at each pulse-beat, of course the water column in the manometer 

 is raised. Fick placed a float upon the surface of the water, and thus enabled the variations in 

 the volume of the fluid to be inscribed on a revolving cylinder. The curve obtained resembled 

 the pulse-curve ; it was even dicrotic. In fig. 118 the movement of the fluid is represented as 

 conveyed to a Marey's tambour, T, similar to the recording apparatus employed in Brondgeest's 

 pansphygmograph (fig. 76). 



The cylinder C may be filled with air. Kries fills it with gas and connects the tube leading 

 to T to a gas-burner. The variations in the gas-flame are then photographed. 



Results. (1) Pulsatile Variations in the Volume. As the venous current is 

 regarded as uniform in the passive limb, every increase of the volume-curve 

 indicates a greater velocity of the arterial current towards the periphery, and vice 

 versd {Fick). The curves registered by the apparatus are volume-pulses, and they 

 resemble the curve of the dromograph (fig. 113, III). The ascent of the curve 

 indicates a greater, the descent a diminished inflow of arterial blood. 



At first sight the plethysmograph curve (volume-pulse, 90, 7) is very like the pulse-curve 

 (pressure pulse) ; both are dicrotic. But there are differences ; the volume pulse-curve beyond 

 the apex falls more rapidly. This rapid fall, which is not accompanied by a corresponding fall 

 of the pressure, is attributed by v. Kries to peripheral reflexion. The dicrotic wave occurs 

 sooner in the volume-pulse than in the pulse-curve. 



(2) The respiratory undulations correspond to similar variations in the blood- 

 pressure tracing (85,/). Vigorous respiration and cessation of the respiration 

 cause a diminution of the volume. The limb swells during straining and coughing, 

 but diminishes during sighing. (3) Certain periodic undulations occur, due to 

 the regular periodic contractions of the small arteries. (4) Other undulations, due 

 to various accidental causes, affect the blood-pressure : changes of the position of 

 a limb acting hydrostatically, and dilatation or contraction of the vessels in other 

 vascular regions. (5) Movement of the muscles of the limb under observation 

 causes diminution of volume, as the venous current is accelerated, the musculature 

 is also very slightly diminished in volume, even when the intra-muscular vessels are 

 dilated. (6) Mental exercise causes a diminution in the volume of the limb, and 

 so does sleep (Mosso). Music influences the blood-pressure in dogs, the pressure 

 rising or falling under different conditions. The stimulation of the auditory nerve 

 is transmitted to the medulla oblongata, where it acts so as to cause acceleration of 

 the action of the heart (Dogiel). (7) Compression of the afferent artery causes a 

 decrease, and compression of the vein an increase in the volume of the limb (Mosso). 

 (8) Stimulation of the vaso-motor nerves causes a decrease, that of the vaso- 

 dilators an increase in the volume (Bowditch and Warren). 



102. TRANSFUSION OF BLOOD. Transfusion is the introduction of blood 

 from one animal into the vascular system of another animal. 



(a) The red corpuscles are the most important elements in connection with the 

 restorative powers of the blood. They seem to preserve their functions even in 

 blood which has been defibrinated outside the body ( 4, A). 



(b) With regard to the gases present in the blood, arterial blood never acts 

 injuriously ; but venous blood overcharged with carbonic acid ought only to be 

 transfused when the respiration is sufficient to oxygenate the blood as it passes 

 through the pulmonary capillaries, whereby venous is transformed into arterial 

 blood. If the respiratory movements have ceased, or are imperfectly performed, 

 the blood becomes rapidly richer in carbonic acid, and in this condition reaches the 

 heart ; thence it is propelled into the blood-vessels of the medulla oblongata, where 

 it acts as a powerful stimulus of the respiratory centre, causing dyspnoea, con- 

 vulsions, and death. 



(c) The fibrin, and the substances from which it is formed, do not seem to play 



K 



