AND CIRCULATION IN FISHES. 



But tliat thefe are the onl^ pafTnges by which the hnrtful mat» 

 ter efcapes feems very doubtfull; as, from Br. rridley's expe- 

 riments it appears, that the colour of the craflamentum of thc 

 blood can be changed by the atmosphere> though the craiTa- 

 mentum be inciufed in an ox's bladder and covered with ferum» 



Sedl. IL 



10. We fhall next tracc the blood from the gills tili it 

 .teturns to the heart» 



ii» In the uppermoft gill (g), which is fingle, there i$ 

 but one confiderable veiu, 



12. In each of the four double gills there are two prin- 

 cipal veins, an upper and under, joined together by a large 

 transverfc canai. 



I -^^ The blood ifliics from both ends of all thefc veins,' 

 but chiefly at the pofterior parc, between the throat and upper 

 part of the fpine. 



14. From the trunks of the branchial veins the blood paf^ 

 fes diredly to all the other p^s of the fish by veifels analo- 

 gous to the branches ot our aorta , and which we therefore call 

 jlrtevies; and the gills and liver are the only organs, which 

 are not fupplied by them folely* 



Sedi. IIL 



15. In the ikate the brmichiat veim join together,' and 

 then difperfe branches in the following order (^)» 



16. The vein A of the uppermofi gill, which is fingle,' 

 is joined by the canal Cy to the uppermofi vein of the fecond 

 gilij and then, running inwards and upwards fornis an «r/^rz/ 



Aa a B, 



ig) Sec Tab. I. fig.jj. A. B. C^ etc. to W. 

 {h) Tab. I. %. 5. 



