100 ORIGINAL ABTICLES. 



K the arm be alloAvecl to remain folded, tlie result will not be 

 satisfactory, as many of the arteries of the arm will probably be bent 

 on themselves, there bein^; articulations in the osseous system of the 

 extremity ; but if the unfolded wing be tied down to a slip of wood, 

 the more favourable position of the trunk and branches of the bra- 

 chial artery wdll cause the injection seldom or never to fail. 



The immortal discoverer of the circulation of the blood, in whose 

 lifetime the existence of the capillary system was not known, sur- 

 mised that part of the arterial blood passed to the veins " per porosi- 

 tates carnis," and part by a direct " anastomosis" between arteries 

 and veins. His spirit may, perhaps, rejoice that the latter of these 

 suppositions has now, at last, been proved to have been not a merely 

 arbiti-ary surmise. 



Microscopic observers of the circulation in the transparent mem- 

 branous web of the bat's wing have mentioned, that the veins in 

 certain distinct localities of the wing may be seen to pulsate like 

 arteries. I shall feel happy if this short note of my researches may 

 explain the true reason of this hitherto unexplained phenomenon. 

 Though pulsation extends not to the capillary vessels, yet physiolo- 

 gists will admit that it must extend to a vein, when that vein is the 

 immediate prolongation of an artery, and the ti'unk of a vein pulsating 

 will, in all probability, cause some of its smaller branches to do the 

 same. 



0. On tlie Ophthalmic Veinjoitiing the Po7'tal System. 



In the tailless Batrachians a very considerable addition to the 

 number of vessels going to the vena portae is to be met with. Among 

 others, the ophthalmic vein sends its blood to the portal system. If 

 the main trunk of the vena portse of a frog or toad be injected — (it 

 is better to open the vein where it passes through the pancreas ; the 

 attachment to this gland serving to keep the vein open ; the injection 

 must be thrown towards the intestines, not towards the liver) — it 

 will be found that all the veins of the pharnyx and of the roof of the 

 mouth have been filled, and hence must, therefore, have belonged to 

 the portal system. These veins form a most complicated network, 

 the main trunks of which are of considerable diameter, so that one 

 might fancy they saw a cavernous structure. The capillary vessels 

 of the mucous membrane of the mouth and pharynx join these venous 

 trunks without any sensible diminution of their calibre (as is the 

 case in other organs), and in addition, they are joined by two large 

 veins, which come out of the floor of the orljital cavities, and are the 

 true ophthalmic veins. The injection, if successful, has entered them, 

 and has filled, likewise, the choroid, iris, and the vascvJar hyaloid. 



It may be mentioned here, that the above alluded to insertion 

 of capillary Acssels into large venous trunks is by no means restricted 

 to the mouth and pharynx. In the testes and ovaries the same 

 thing occurs, for the capillaries of these organs meet large venous 

 blood-vessels which surround the germinal follicles in the ovary, or 



