436 Proceedings of the British Association. 



of the second circumstance, or the direction, he adverted to the tor- 

 tuous entrance of the internal carotid and vertebral arteries into 

 the skull in the human subject, and shewed that it is still more re- 

 markable in the horse, which in feeding requires to have the head 

 for a considerable time in the dependent posture. But the best ex- 

 amples of the tortuous or serpentine course, are to be seen in the 

 spermatic arteries of the mammalia. This mechanism, he contend- 

 ed, adapts the circulation to the various positions in which organs 

 may be placed, and to their states of action and repose. In speak- 

 ing of the third modification, or the subdivision into numerous long 

 branches, he particularly alluded to the observations of Sir Anthony 

 Cal-lyle with respect to the arteries of the sloth, and shewed that a 

 similar ramification is found in the hedgehog, both in the arteries 

 of the panniculus camosus and of the mesentery. Of the last mo- 

 dification, the plexus, he shewed examples in the rete mirabile of 

 Galen in the internal carotid, and of Hovius in the ophthalmic ar- 

 tery, of the ruminantia. He inferred that this structure prevents 

 vascular turgescence, which would otherwise occur, during the long 

 period when these animals keep their head in the dependent posi- 

 tion while browsing. He also shewed that a rete mirabile exists 

 in the ophthalmic artery of the seal and goose, and considered it 

 probable that in them it is conducive to the alternate adaptation of 

 the eye to vision in air and water. He described the remarkable 

 plexiform arrangement which exists in the mesenteric arteries and 

 veins of the hog ; and instituted a comparison between these ves- 

 sels in carnivorous and herbivorous mammalia, concluding that 

 these modifications are in conformity with the transmission of the 

 blood through the liver, the rapidity of the peristaltic motion, and 

 the power of nutrition. 



Dr Hodgkin read a part of the history of the results of the ex- 

 perimental inquiry respecting the action of poisons, the prosecution 

 of which was committed by the Association at its last meeting to 

 himself and Dr Roupell, so far as he himself had been able to pro- 

 secute the inquiry. Conceiving the object which the Association 

 had more particularly in view in calling for this report, to have 

 been to facilitate the recognition of the eft^ects of acrid poisons, with 

 a view to aid in judicial inquiries, Dr Hodgkin considered it as an 

 essential preliminary, to obtain an accurate and definite knowledge 

 of the different appearances which are presented by each part of 

 the alimentary canal witliiii the limits compatible with health; and 

 accordingly, in the first part of liis report, he entered at considera- 



