342 Prof. W. Jones on the Caudal Heart of the Eel. [May 7, 



pound, this property is also possessed by the CO and N2 O3 compounds of 

 haemoglobin, as well as by the nitrite compounds of oxidized haemoglobin. 

 It is probable that we may now find that a large number of condensed bodies 

 have the property, like the nitrites, of forming combinations with the blood- 

 colouring-matter. 



II. Microscopical characters of the rhythmically contractile 

 Muscular Coat of the Veins of the Bat^s Win^^ of the Lym- 

 phatic Hearts of the Frog^ and of the Caudal Heart of the 

 Eel. In Three Parts. — Part I. Microscopical characters 

 of the rhythmically contractile Muscular Coat of the Veins 

 of the Web of the Baf s Wing.^' By Thomas Wharton Jones, 

 Professor of Ophthalmic Medicine and Surgery in 

 University College^, &c. Received April 8^ 1868. 



(Abstract.) 



This is Part I., of a series of three, of a paper on the microscopical 

 characters of rhythmically contractile muscular tissue, other than that of 

 the blood-heart. It comprises a reexamination of the microscopical cha- 

 racters of the rhjthmically contractile muscular coat of the veins of the bat's 

 wing, and is offered by the author as Appendix No. 3 to his paper in the 

 Philosophical Transactions for 1852, entitled "Discovery that the veins of 

 the Bat's Wing (which are furnished with valves) are endowed with rhyth- 

 mical contractility, 'and that the onward flow of the blood is accelerated 

 by each contraction." This reexamination supplies additional details, 

 illustrated by more correct figures, confirmatory of the author's previous 

 description of the microscopical characters of the muscular coat of the 

 veins of the bat's wing. The author examines also, byway of comparison, 

 the tonically contractile muscular coat of the arteries, and points out that, 

 though the fibrils of the muscular coat of the veins do not present trans- 

 verse markings, they differ in their microscopical characters as much from 

 the fibrils of the muscular coat of the arteries, as the transversely striped 

 muscular fibrils of the bat's heart do from them. He insists, therefore, 

 in conclusion, that there are no grounds for an implied physiological form 

 of the doctrine of isomerism, viz. similarity of structure, with different 

 endowments. 



Part II. ^' Microscopical characters of the rhythmically con- 

 tractile Muscular Coat of the Lymphatic Hearts of the Frog.^^ 

 Beceived April 13, 1868. 



The author, in this second part of his paper, first calls attention to the 

 fact that, on viewing the anterior lymphatic heart from the front, after 

 dissecting down upon it from the back, he sometimes found its cavity 

 filled with air or blood. The way by which the air or blood had entered 



