40 
DR. PETTIGREW ON THE MUSCULAR ARRANGEMENTS 
symmetrically, and so nicely balanced as regards length, strength, and direction, that I 
am of opinion the order of contraction is very precise and well defined. I am further 
inclined to believe that the fibres of the several layers contract towards certain points, 
the more longitudinal anterior, posterior, and lateral fibres contracting from above 
downwards in the direction of the urethra so as to approximate the apex and fundus, 
the slightly oblique, oblique, and very oblique spiral fibres contracting towards the 
points where they cross each other, viz. towards the anterior, posterior, and right and 
left lateral raphe. That this centripetal and downward action of the oblique fibres to- 
wards the points of intersection takes place is rendered probable by the fact, that in the 
contracted bladder the anterior, posterior, and lateral ridges (where they exist) are thrown 
into bold relief*, the sides of the viscus in some instances coming together so com- 
pletely that their mucous surfaces adhere. In such cases, if any urine be present, it 
is, as a rule, confined to the immediate vicinity of the uretral orifices, and not diffused 
throughout the cavity of the bladder generally, as it would most likely be if there were 
not a strong persistent lateral action. 
Explanation op Plates. 
PLATE III. 
Fig. 1. Anterior view of young adult male bladder, showing longitudinal {ah), slightly 
oblique (c d ef), oblique {g h ij), and very oblique {Tclm n) spiral figure-of- 
eight fibres, as seen in layers 1, 2, 3, & 4. 
x. Urachus. 
Fig. 2. Anterior view of adult female bladder. Shows slightly oblique ( c d ef) and 
oblique (g h ij ) spiral figure-of-eight fibres, with a few oval fibres, as observed 
in layers 2 & 3. 
x. Urachus. 
Fig. 3. Anterior view of adult female bladder (walls rendered transparent). Shows 
longitudinal and slightly oblique spiral figure-of-eight fibres mixed up {a h), as 
seen in layers 1 & 2. Likewise the very oblique spiral fibres commonly 
regarded as circular {Jc l), forming the fourth or central layer. 
Fig. 4. Posterior view of young adult male bladder, showing longitudinal {op), slightly 
oblique {q t), oblique (uvw x), and very oblique (yf, z z') spiral figure-of-eight 
fibres, as seen in layers 1, 2, 3, & 4. 
2 , 2 . Portions of ureters. 
Fig. 5. Posterior view of adult female bladder (transparent). Shows longitudinal 
{op), slightly oblique {q t), and very oblique or circular fibres {yz), as seen 
in layers 1, 2, & 4. 
Fig. 6. Posterior view of adult male bladder. Shows longitudinal (o), slightly oblique 
* Vide Plate IV. figs. 34, 36, & 38, ah, op, st. 
