22 FISCHER ON THE PELVIS OF THE MAMMALIA. 



The symphysis of the pubis is in them, with the exception of the didelphisj 

 either very short or sometimes evidently wanting ; the bones of the ischium, 

 as in the genus mus, are flattened, very broad, thin, and the position of the 

 tuberosities is nearer to the promontary, than are the angles in which the de- 

 scending rami of the pubis meet with those of the ischium. The pelvis of the 

 hedgehog, at the symphysis of the pubis, is remarkable for a wide hiatus be- 

 tween the bones, nor is this opposite to the acetabulum, but much lower down, 

 and seems to arise from a very acute union of the rami of the pubis and 

 ischium ; it remarkably resembles in form the pelvis of birds, as of the pigeon, 

 &c. ; on the other hand, the pelvis of the mole, by the union of the os 

 sacrum and ilium into a single osseous lamina, seems also to pass partly into 

 the form of the pelvis of the bird. We have already noticed the distinguish- 

 ing characters in the pelvis of the bats (Aiitenreith) . 



Section 22. 7. Solidungula. As the horse is the most important of all the 

 animals connected with the veterinary art, I shall dwell longer on the descrip- 

 tion of its pelvis. Five vertebra? compose the os sacrum, which in youth are 

 both separated and connected by cartilages ; by degrees, however, as the car- 

 tilages ossify they become contiguous, so that at last no vestiges of their 

 original separation remain. The os sacrum shows two margins, and two sur- 

 faces a superior or external, and an inferior or internal ; also a base and apex 

 to be considered separately. The broad margins anteriorly show a consider- 

 able surface, full of tuberosities and little depressions, serving to unite it with 

 the os ilium ; this surface of the margins is called by some the sigmoid or 

 semilunar aspect. The external, or superior convex surface, is tuberous, and 

 furnished with several prominences : in the middle there arise five separate 

 and distinct spinous processes ; the second of these is the longest, but it is also 

 the slenderest : the rest gradually decrease in size and thickness, terminating 

 in a quadrangular little head in the apex. I have often found these spinous 

 processes united together. Between the bases of these processes there are 

 four foramina, communicating- with the vertebral canal. Close to these, on 

 each side, there are other four foramina, which also lead into the vertebral 

 canal. The inner, or inferior surface of the sacrum, is concave and without 

 tubercles. Near the margins it is perforated by four foramina ; between each 

 pair of these holes there is an elevated transverse line, the remains of the 

 former intermediate cartilages. The anterior portion of the base of the sacrum 

 is the broadest ; in the middle of this base is a broad, oval, articular surface. 

 Above this articular surface, is the triangular opening of the canal of the 

 sacrum passing throughout its whole length ; this is a continuation of the 

 vertebral canal. Close to the aperture of this canal, there arise two oblique 

 processes each an inch long, and having the same direction as the correspond- 

 ing processes of the lumbar vertebra?. On each side of the sacrum, and towards 

 the side of the articular surface, there arise two large prominences which unite 

 with the transverse processes of the last lumbar vertebra ; by some these are 

 called the articular tuberosities. On the apex of the os sacrum may be ob- 

 served a small, oval, articular surface, connecting this bone to the first coccy- 

 geal vertebra. 



Section 23. The coccygeal vertebrae vary much in number. The usual 



