Dr. Burnett on the Renal Organs of the Vertebrata. 381 
these organs in Fishes have been regarded as merely permanent 
forms of the above mentioned bodies. This last, however, I @o 
not think correct, for in be class the subsequent phases of de- 
velopment by which the organ is increased in size, are exactly 
like those of the general pact of these organs in Birds and 
Mammals. 
_ The formula of development is the branching ~— in spe! 
of a primitive tube which is the future ureter ;—the | por- 
tions of these branches forming an intimate schletion with the 
general vascular a either by Malpighian bodies, or by a del- 
icate net-work of vessels. 
The mode of jbettmtions is therefore arborescent, and the anal- 
ogy of the development and growth of this s gland with that of 
vegetable forms is too striking not to be noticed. We shall see 
that the growth exactly resembles that of a tree even sco ks in 
its details. 
The line of development being everywhere the same, I will, 
for the sake of uniformity, describe it as occurring in the Chick, 
where, moreover, I have carefully registered the successive phases. * 
In the chick no traces of the kidney are perceptible, according 
to my own observations, until Soa end of the fourth or the begin- 
ning of the fifth day. The ureter, then, is the part first seen, 
and consists of a simple tube, ne upper part of which sends off 
branches. Each of these branches then divides and subdivides, 
* Here T may poe hoe a to the views of other oleate who hay e spe- 
cially studied the deve lopment of the kidney. th authors best wn in this re- 
—— Rathke, ae Valentin wae d as well also as Wit “ich of later times. 
orks of these men have alrea y been cited, According to Rathke, the first 
traces, of the ki ing ein a a number of small claviform protuberances appeari g 
quently appear, but in a manner ee pr ome Re pier ne 
alentin’s Uoleations agree in general with those of Rathke, but, from some 
‘p \ 
squeal Pa Vale niin’ view of t ormation of the uriniferous tu 
Ades with that of Henle, viz.: that it ao by the condensation of a linear arrange- 
ment of the vesicular contents of the 
Both Miiller and Bischo off con ae in ional vi views be oe but Bischoff 
differs not a little upon some points which dese: He says, “I have 
never been able to convince ing hat the ureter, ; pelvis, ae canaliculi are he 
Sped se rl ely, and : think that their ru diments e continuous throughout. ‘ae. § 
©pmen; 
But ot Goh results most closely approach my own. Speaking of these 
organs in mphibia, he says: “ The further growth of the kidney occurs, it would 
ily by a aed deverticulation of the ex eretory “see eae and partly 
ening, lengthening and branching of the primitive dev 
ill n in the text, t he view ! ngs nee is the arbo iss mode of devel- 
oe c d accordi the class, of these organs—the formula 
being a more or less extended oes Pa of tubes from a Pk a a duct. 
_ Stoowp Seems, Vol. XVII, No. 51.—May, 1854. oe 
