MYOLOGY OF THE ORNITHORHYNCHUS. ] 33 



rib it becomes invested with a glisteniug aponeurosis, at first sight 

 plain and single, but readily resolvable (more especially a little higher 

 up) into a series of oblique fascial tendons running inward and up- 

 ward, with pretty definite insertion into apfces of successive trans- 

 verse processes ; the arrangement is clearest at the top of the thorax 

 but is essentially the same throughout. Now on raising the outer 

 border of the whole muscle, and dividing successive costal attach- 

 ments so as to reflect it over towards the spine and expose its under 

 surface, a perfectly regular series of teudiuo-muscular slips is brought 

 to view. Counting 2-3 lumbar ones, there are about 14 in all, aiising 

 distinct and tendinous, from transverse processes, passing obliquely 

 upwards and outwards. These are best displayed along the middle 

 of the back ; they terminate opposite the 3d and 4th ribs, at least as 

 far as longissimus dorsi is concerned, being transferred to the outer 

 (costal) branch of the erector {i. e., cervical prolongation of sacro- 

 lumbalis = "transversalis colli")- Above this point the longissimus 

 dwindles into characters of semi-spinalis dorsi et colli ; and the few 

 muscular-tendinous fibres pass obliquely downward and outward, in- 

 stead of upward and outward, like those of the back. External to 

 these, "transversalis colli" lies along the side of the neck, betwixt 

 the digitate insertion of the trachclo-mastoid and the " cervical is 

 ascendeus," blending with both of these. It may be said to arise from 

 the most prominent transverse processes of cervical vertebrie, by ten- 

 don scarcely separable from that of the c. asc.endens ; it passes down- 

 ward and obliquely backward, ending with longissimus opposite the 

 3d and 4th ribs, with fascial attachments all the way. 



Sacro-lumhalis. — This is the outermost of three diflferent planes 

 that may be distinguished in the loin (longissimus making a fourth). 

 It is there a thin fan-shaped plane, taking definite origin from the 

 tip of the ilium, and passing upward spreading over the ribs. This 

 costal expansion is continuous over the whole length of the thorax 

 (with no diff"crentiation into "muse, accessorius"), and entirely sep- 

 arate from any part of the longissimus ; it is wholly costal, without 

 vertebral attachment. It is an inch and a half broad at its widest 

 part; its outer border is very convex, and runs a little back of the 

 line of the digitations of the obliquns abdominis ; its inner or pos- 

 terior border is straight, and corresponds with the outer border of 

 the longissimus ; the plane is very thin, and intimately attached to 

 each rib as it passes over it ; to the eye, in fact, it resembles a set 

 of supernumerary intcrcostals, with perpendicular instead of oblique 

 fibres; we should judge it to be more of a respiratory muscle than a 

 back-straightener. Towards the top of the thorax it grows narrower, 

 and becomes, on the neck, cervicalis ascendens, dillercntiatcd from 

 other nuchal muscles by the iutei"vention of trachelo-mastoidcus, and 



