PHOFESSOU nYETl/s ANATOMICAL NOTES. Q9 



The aorta contains mixed blood ; when this blood, therefore, is so 

 brought to the lungs, the venous portion of it is oxygenated, and 

 then this ox3^genated product goes to the vena porta?. This is an 

 extraordinary fact, and cannot, I think, be physiologically understood, 

 so long as we loiow so little of the chemistiy of the production of 

 bile in reptiles. 



In all those genera of short-bodied snakes, where the pulmonary 

 branches of the aorta are wanting, there are, in addition to the pul- 

 monary vein to the aviricle, three to five small pulmonary veins going 

 direct to the vena portse. The necesKsity for arterialized blood in the 

 organ supplied by this vein is therefore placed beyond a doubt. 



8. 0)1 tlie Hadial Artery in the Cheiroptera. 



A very curious anatomical fact, and one not devoid of physiological 

 interest, is to be found in the membranous expansion of the ' wing' 

 of the bat. It consists in the immediate transmission of arterial 

 blood into a. venous trunk, without the intervention of capillary 

 vessels. This I have found to be the case in the following genera: — 

 Plecotus, Vespertilio, Hhinolophus, Pteropus, Noctula. 



Inject a bat, through the aorta, with a coarse injection material 

 (specimens from abroad, which have been long preserved in spirits, 

 reqviire a somevv'hat finer material), which you are siu-e will not too 

 easily enter the capillary system. The wings ought to be extended, 

 so as to facilitate the passage of the fluid through the brachial artery 

 into the arteries of the arm and hand. Even should the injection 

 meet with but a very second-rate success, still it will be found that a 

 large vein will be also filled. This vein imns along the free margin 

 of the fold of the integument, and extends from the shoulder joint to 

 the carpus. 



This vein is the somewhat modified vena cephalica of man and the 

 other mammalia. A very careful investigation as to where the artery 

 ends and the ^'ein begins, shows us that the radial artery, whicli 

 tends towards the metacarpal bone of the thumb, describes a circle 

 round the base of the thumb, from its palmar to the dorsal side, and 

 is, on reaching the back of the hand, reflected towards the forearm, 

 as a vein (vena cephalica) which takes its way between the two 

 layers of the before alluded to fold of the integument to the arm-pit, 

 where it terminates in the vena axillaris. 



Before becoming a vein, the radial artery sends off the requisite 

 branches for the nutrition of the parts in connection with the elon- 

 gated metacarpal and phalangeal bones ; but, at the same time, its 

 real termination is not to be sought for in the capillary system, but 

 in the peculiar manner I have just referred to ; for, owing to having 

 used a coarse injection, no capillary vessels have been filled, and yet, 

 notwithstanding, a venous trunk (larger than the vena brachialis 

 itself) is filled up with the injection material, throughout eitlier the 

 whole or entire of its length (reckoning from the thumb). 



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