476 Proceedings of the Royal Fhysical Society. 



As yet, after a patient search, no micro-organisms have 

 been found, but the evidences of their presence at some time 

 or other as seen in the changes in the tissue elements are 

 very strong indeed. 



Description of Plates XXIII. and XXIV. 



FIG. 3. 



Longitudinal section through small healthy artery taken from base of Fin 

 of Cod. Preserved in Miiller's fluid stained with picro-carmine ( x 300). 



{a.) Timica adventitia, or outer connective tissue coat, composed of white 

 iibrous tissue forming dense felted wavy mass. 



{h. ) Tunica media, or middle coat, composed of circular non-striped muscular 

 fibres. The nuclei and outlines of the fibres, cut transversely, well seen at the 

 upper part of the figure ; the outlines of the circular fibres are well seen. 



(c. ) Tunica intima, or inner coat ; the laminated fibrous tissue well seen, but 

 the flattened connective tissue and endothelial cells are not shown in the 

 drawing. 



A few nucleated blood corpuscles are seen lying in the lumen of the vessel. 



FIG. 4. 



Transverse section across two branches of a small artery just below the 

 point of bifurcation of the parent vessel in the thickened gelatinous margin 

 of the ulcer at the base of the Fin ( x 80), stained in picro-carmine. 



A. In this branch obliteration is not complete. 



(a.) Infiltrated adventitia, especially around the small vasa vasorum. 

 {b.) Muscular coat little changed. 



(c.) Inner coat, irregularly thickened. Here the cells lying between the 

 fibres are well seen and also the axis in Avhich they lie. 



B. In this branch the obliteration is complete and degeneration has 

 commenced. 



{d.) Altered muscular coat. Muscular fibres atrophied or degenerating. 

 Increase of interfibrillar nuclei, 



(c.) The vitreous inner coat is here very well seen. 



FIG. 5. 



Section through small part of wall of vessel. (Plate XXIV. , Fig. 4 A. ) x 400. 



Here the enormous proliferation of the cells of the inner coat is well seen. 

 " (a.) Represents position of lumen of vessel. The endothelial layer has 

 been removed. 



(&.) Represents laminated layer with axis of cells at right angles to 

 circumference. 



(c.) Muscular coat. 



In this part of the vessel the degenerative changes have not yet commenced. 



