CIRCULATION AND FOOD. 135 



We find, on the contrary, that the more they are covered, especially 

 with solid bodies, the more the pulsation is felt ; viz. in tumours covering 

 the carotid, &c. 



There is certainly a pulsation in veins J ; for, when we bleed a per- 

 son in the hand or foot, we evidently see a strong jet ; much more in 

 some than in others, and much more than in the bend of the arm. The 

 query is, does this arise from the immediate stroke of the heart, or is it 

 by the lateral pressure occasioned by the swell of the arteries ? To 

 ascertain this the better, it is necessary to observe several things. [One 

 of these is, that] the veins on the back of the hand are superficial and 

 not surrounded with vascular parts : but still it may arise from the 

 impulse given to the blood in the smaller arteries occasioning their 

 lateral swell, and that this acceleration given to the blood's motion in 

 the smaller veins is communicated to those on the back of the hand. 

 But I think I have seen the difference in the projection so great, as hardly 

 to arise from that cause alone ; and if this were the whole cause we should 

 have it in some degree in every vein ; for every vein is in some degree 

 surrounded, and of course in some degree affected by the swell of the 

 arteries of the part ; but we certainly do not observe it in so great a 

 degree in the bend of the arm. 



The veins in the spleen of a dog do not anastomose. I tied up one 

 of the veins going to one end of the spleen ; that end immediately be- 

 came turgid and of a dark red, while the other end remained flaccid and 

 of the former colour. 



The spleen is the reddest, part of any in the animals of those classes 

 which have red blood ; so that there is more red blood in the spleen 

 than in any other part. 



Of Food. 



Food may be divided into two sorts ; viz. that which is wholly dis- 

 solvable in the stomach, and that which only yields its juice. 



The first is the most profitable, and includes all animal food, ex- 

 cepting cuticle, hair, nails, horns, &c. ; [it also includes] roots without 

 the skin, all fruits without the skin, and all seeds without their skin 

 or husks. 



The second includes all the other parts of vegetables that have not 

 been mentioned above, such as the wood and leaves. Many yield so little 



1 [Flourens observed in the venous trunks of frogs alternating movements of con- 

 traction and dilatation : Midler is inclined to attribute this to the influx of the lymph 

 propelled by the lymphatic hearts ; but Flourens thinks the veins he observed to 

 beat were too remote from the lymphatic hearts to be so influenced. Jones has ob- 

 served a pulsation in the veins of the bat's ear.] 



