AND CIRCULATION IN.FISHES. . 187 
Rüt that thefe are the only paffages by which the hurtful mat- 
ter efcapes Ícems very doubtfull; as, from Br. Priflley's expe- 
riments it appears, that the colour of the craffamentum of the 
blood can be changed by the atmosphere, though the craffa- 
mentum be inclufed in an ox's bladder and covered with fervun, 
BA Sed; IT. ; 
1o. We fhall next trace the blood from the gills til it 
:*feturns to the heart, j 
C3. In the. uppermoft gill (g), which is fingle, there is 
but one confiderable vein. 
- 12. In each of the ddr double gills there are (vo prit: 
cipal vem, an upper and under, joined together by a sare 
transverfe canal, 
13. The blood iffues from both ends of all thefe veins; 
but chiefly at the pofterior puts " between the Be and uppet 
pu of the fpine. 
. 14. From the trunks of the branchial veins the blood paf- 
fes directly to all the other parts of the fish by veffcls analo- 
cos to the branches of our aorta, and which we therefore call 
Zr "tris; and the gills and liver are the only organs, which 
arc not fa pplied by them folely, ; 
Sect, TIT, 
: In the fkate the branchial veius join n togeer] and 
then difperfe branches in the. following order (4). 
16. 'The vein A of the uppermoft gill, which is fi ngle, 
is joined by the.canal Cy to the uppermoft vein of the fecond 
gil; and then ; running inwards and üpwards forms an azzeryj 
Àa 2 um B5 
(g) See "Tab. I. fig.(5. A, B. C, etc. to W. 
b "Tab. 1. fig. 5. " 


