chap, xi.] SNAKES : SCALES. 277 



is described by Studer, Mitth. natur. Ges. Bern, 1869, p. 24, as 

 having 20 rows. This specimen was unusually dark in colour. 

 [The presence of an even number of rows is in itself remarkable, 

 but it is not stated whether this total was reached by duplicity in 

 the median dorsal row or by inequality on the two sides.] 

 406. A specimen of Snake from Morocco closely resembled Macropro- 

 todon mauritanicus Guichenot (= Lycognathus cucullatus Dum. 

 Bibr.), but differed from it in having 23 rows of body-scales 

 instead of 19, being 4 rows in excess of the normal number. 

 Peters, W., Sitzb. Ges. naturf. Fr. Berlin, 1882, p. 27. 



For particulars as to the range of variation in these numbers 

 in different species, see numerous examples given by Botjlenger, 

 G. A., Fauna of Brit. India : Reptilia and Batrachia, 1890. 



Kidneys ; Renal Arteries ; Ureters. 



Meristic Variation in these organs is well known and the 

 principal forms found are described in most text-books of anatomy. 

 Some information as to these is given below. The examples are 

 all from the human subject. 



407. Kidneys. Male having three kidneys. The left kidney was 

 normal in shape, position and consistency but was abnormally 

 large. The right kidney was placed opposite to it and weighed 

 only half as much as the left. From it a ureter with a small 

 lumen arose and passed in a normal course so far as the division 

 of the aorta. At this point its course lay along the surface of the 

 third kidney. This third kidney lay over the whole right iliac 

 artery, a portion of the right crural artery for the space of 9 lines, 

 the right crural vein and the psoas major muscle. It was larger 

 than the upper right kidney and had the form of an oval with its 

 ends cut off. The anterior and posterior surfaces were convex. The 

 anterior surface was grooved for the passage of the ureter men- 

 tioned above, which received the ureter of the second kidney and 

 passed normally into the bladder. The man was a sailor and died 

 of enteritis at the age of 39. Thielmanx, C. H., Midlers Arch, 

 f. Anat. u. Phys., 1835, p. 511. 



408. Renal Arteries. The number of the renal arteries in Man is 

 liable to great variation. In specimens in which the kidneys are 

 normal in position the arteries may be (a) diminished or (b) 

 increased in number. The latter is much more common. 



Multiple renal arteries may be threefold, (a) Most commonly 

 the additional branches spring from the aorta, (b) they may come 

 from other sources ; or (c) there may be a co-existence of additional 

 vessels from both sources. 



