Dr. Barry on the Blood Corpuscles. 375 



vous cord, this vessel is gradually lessened in size, until it arrives at 

 the terminal ganglion of the cord in the tail, where it is divided into 

 two branches, which take the course of the terminal nerves, and 

 these are again subdivided before they arrive at their ultimate distri- 

 bution. In addition to these parts, the author found a hollow fibrous 

 structure, which closely surrounds the cord and nerves immediately 

 after they have passed beneath the arch of the thorax. From the 

 sides of this structure there pass off backwards two pairs of vessels, 

 that get beneath the peritoneal lining of the abdominal cavity and 

 are distributed on the first pair of branchiae. A small vessel also 

 passes backwards be«eath the cava, and, being joined by anasto- 

 moses from the spinal artery, form the commencement of a vessel 

 which the author formerly described in the * Medical Gazette' as the 

 subspinal vessel. This vessel, extending along the under surface of 

 the nervous cord, communicates directly, by short vessels, with the 

 supra-spinal artery, and gives off, at certain distances from its under 

 surface, several large vessels, which unite with others that convey 

 the blood which has circulated through the abdominal segments, di- 

 rectly to the branchiae, whence it is returned to the heart by many 

 minute vessels that originate from the posterior internal part of each 

 branchia, and, united into single trunks, pass around the sides of the 

 segments to the valvular openings on the dorsal surface of the heart. 

 In the tail of the Scorpion there is a direct vascular communication 

 between the caudal artery and the subspinal vein, which, from the 

 direction of the vessels, induces a belief that there is some peculi- 

 arity in the circulation of the blood in this part of the body. Be- 

 sides these vessels, the author found an arterial trunk that originates 

 from the commencement of the aorta as it descends into the thorax. 

 This vessel passes backwards along the alimentary canal, to which 

 it is distributed, and gives off branches to the liver. 



This paper is accompanied by five drawings, illustrating the ana- 

 tomical facts which are described in it. 



May 11. — The following papers were read, viz. — 



1. "Variations de la Declinaison et Intensite Horizontale mag- 

 netique observees a, Milan pendant vingt-quatre heures consecu- 

 tives le 22 et 23 Mars, et le 19 et 20 Avril 1843." Par F. Carlini, 

 For. Mem. R.S. 



2. " Note regarding the Observations of T. Wharton Jones, Esq., 

 F.R.S., 'On the Blood Corpuscles*.'" By Martin Barrv, M.D., 

 F.R.S. L. & E. 



The author observes, that the structure of the blood-corpuscles 

 can be accurately learned only by a careful investigation of their 

 mode of origin, and by following them through all their changes in 

 the capillary vessels, and especially in the capillary plexuses and di- 

 latations, where all their stages of transition from the colourless to 

 the red corpuscles may be seen. The filament which forms here 

 and there in the corpuscles of coagulating blood he has shown to 

 other persons, with Microscopes made by Ross and Powell. Dr. 

 Barry denies that he meant certain general remarks in his paper, re- 

 [• See Phil. Mag. S. 3. vol. xxii. p. 480.] 



