AND BLOOD PRESSURE 149 



Pleasurable feelings are accompanied by relaxation of the muscles 

 of the limbs and dilatation of the vessels of the limbs relaxation 

 in contrast to the strained taut condition of icork. It is not the 

 brain, as Mosso supposed, but the belly within which the blood 

 collects during mental effort. The brain, limited in its expansion 

 by the rigid cranial wall, contains a quantity of blood which can 

 vary but little, except when the tissues of the brain actually lose 

 or gain water, and so shrink or swell. Rise of arterial pressure 

 produced by the contraction of the splanchnic area does not 

 expand the brain so much as increase the proportion of arterial 

 blood to venous blood within it and accelerate the velocity of 

 flow. In muscular exercise the limbs receive more and the venous 

 cistern in the abdomen contains less. The stagnation of the blood 

 in the abdominal veins and liver during mental work and the 

 sluggish circulation caused by the arm-chair posture must have a 

 direct bearing on the irritable dyspepsia of brain-workers. Was 

 not Thomas Carlyle cured of his by horse riding ? Exercise 

 sweeps the body clean of unoxidised food stuffs by the swirling 

 current of blood and the greatly increased rate of metabolism. 

 The breathing volume of a boxer after a three minutes bout may 

 go up from the resting volume 9 to 40 litres per minute. How the 

 muscles must squeeze the blood in his organs and drive it to the 

 right heart ! 



THE FILTRATION HYPOTHESIS 



In the explanation of physiological and pathological processes 

 capillary pressure has been since the teaching of Ludwig constantly 

 evolved as a deus ex machina for producing filtration. Thus the 

 glomerular capillaries have been generally supposed to filter water 

 and salts into the renal capsules under the pressure of the blood, 

 which is supposed to be higher than that of the urine in the renal 

 tubule. Similarly in dealing with the formation of lymph, filtra- 

 tion by capillary pressure is supposed to be an important factor, 

 b a school of physiologists of whom Starling and Cohnstein in 

 the past have been chief exponents. Dropsy and oedema, such as 

 occur in cardiac incompetence, have been attributed to filtration 

 brought about by increased capillary pressure ; an altered per- 

 meability of the capillaries being admitted as an accessory patho- 

 logical factor in the explanation of the fact that increased vascular 



