26 
DR. PETTIGREW ON THE MUSCULAR ARRANGEMENTS 
of the bladder, I have confined my remarks to elucidating the plan or general arrange- 
ment, and have trusted for minor details to the figures and diagrams which will, I trust, 
be found sufficiently numerous for this purpose. 
EXTERNAL FIBRES. 
First or superficial layer , consisting principally of longitudinal fibres. — When the 
bladder of a young adult has been distended and carefully divested of its blood-vessels, 
nerves, and cellular tissue, it is found to be bilaterally symmetrical, the fibres comprising 
its parietes pursuing complicated but definite directions. 
On the anterior aspect a certain number on either side of the mesial line proceed in a 
nearly vertical direction from the cervix to the urachus, and have from this circumstance 
been termed longitudinal (Plate III. figs. 1 & 3, a b; Plate V. diag. 1, a b). Of these, 
some arise from the posterior surface of the pubes by means of the anterior true liga- 
ments, and some from the upper or dorsal surface of the fibrous capsule investing the 
prostate (Plate IV. fig. 29, ab), a certain number proceeding from the dorsal surface of 
the urethra (a). Others (Plate IV. fig. 28, a) pass in a more or less horizontal direction 
through the gland, and in this manner reach the under or ventral surface (c) of the 
prostatic capsule to which they adhere, the greater number losing themselves in the 
glandular stroma (f). In the opposite direction, or towards the urachus, some of the 
fibres are continuous with the urachus itself, while others are inserted into the peritoneal 
fold investing the top of the bladder. The greater proportion curve over and become 
continuous with the vertical or longitudinal fibres posteriorly (Plate III. figs. 4, 5, 6 & 
8, op). The posterior longitudinal fibres in their turn are connected with the fibres of 
the compressor urethrae, the under or ventral surface of the fibrous capsule of the pros- 
tate (Plate IV. fig. 29, op), and the ventral surface of the urethra (w). Of these, a cer- 
tain number curve in an upward direction (Plate IV. fig. 28, hi) and pass through the 
gland (f) to reach the dorsal surface of the prostate. The anterior and posterior longi- 
tudinal fibres, as they appear on the dorsal and ventral surfaces of the prostatic portion 
of the urethra, are seen at b and p of figs. 1 & 4, Plate III. On the right and left lateral 
aspects of the bladder longitudinal or vertical fibres, similar to those occurring on the 
anterior and posterior aspects, can be detected (Plate IV. fig. 9, a b) ; and I regard 
their occurrence in these situations as favouring the idea that originally the bladder is 
formed from the intestine. The fourfold arrangement of the fibres, especially at the 
apex and base, is well seen at Plate IV, fig. 16, ao, hi; fig. 18, bp, mn. The lateral 
longitudinal fibres are attached to the fibrous capsule of the prostate on its right and left 
aspects, some continuing their course on the sides of the urethra (Plate III. figs. 7 & 
8, b), while others pass through the gland transversely (Plate IV. figs. 33 & 35, ac), 
or become lost in its substance. Sabatier*, when speaking of the anterior longitudinal 
fibres, says that in some instances this layer is extended laterally, and that in such cases 
the internal border of the aponeurosis of the levator ani also serves for insertion. 
* Op. cit. 
