Anatomy of Seat. 



275 



which form the junction of the pelvis with the thighs, which are parallel with the hip-bones 

 and the tail-bone. 



This seat has been more successfully described in the following extract from a letter from my 

 friend Dr. John Reeve, of Great Marlborough Street, Regent Street :— 



THE SEAT ON HORSEBACK ANATO.MICALLY CONSIDERED. 



"What is a man to sit on.' Well, he has two bones in his pelvis* (the sitting bones) — 

 each one is anatomically described as the Os ischium, or sedentarem — and a third in the posterior 

 portion of the pelvis, called the Os sacnmi (or 

 sacred bone). The Os coccygis is a small bone 

 at the end of the sacrum, and is said to resemble 

 in shape and size the cuckoo's bill ; it is the 

 rudimentary tail bone,t and is highly developed 

 in tailed animals. 



" The two sitting bones in front, with the 

 sacrum behind, form a sort of triangular base for 

 the human seat on horseback. 



" If the rider sits in his proper place, he 

 will mainly rest on the two sitting bones, and 

 partially at times on his sacrum. He may thus 

 be said to rest on a triangular basis, a seat 

 affording the greatest degree of comfort. 



" If, however, the rider throws his thigh 

 and leg forward too much towards the horse's 

 shoulder, the sacrum, which forms the posterior 

 portion of the bony triangle, will come in too 

 much contact with the back of the saddle. 



" Finally, if the rider throws his thigh and 

 leg too much back towards the horse's tail, he 

 must then necessarily sit on the front part of 

 his sitting bone (the perineum), a position of dis- 

 comfort and even danger." 



" The only firm and steady seat is on this 

 triangle." The Monboddo bone (the tail bone) 

 must neither be over-weighted nor made too con- 

 spicuous. " No good rider sits on his fork, but 

 on his seat." 



How this seat is to be obtained depends 

 on the conformation of the man. The round, 



short-thighed man will have more difficulty in fitting himself to his saddle and settling the 

 length of his stirrup-leathers than the born horsemen who win steeplechases. For this purpose 



* See diagram of part of skeleton. 



t Hudibras, boasting to his lady-love, says :— 



*' I am no horse, 



That I can argue and discourse ; 



Have but two lefjs, and neer a tail.'' — Part ii., Canto i. 



DIAGRAM SHOVVINU FRONT VIEW OK THE PELVIS 

 (IN A STANDING POSITION). 



I. The Os ilium (hip or haunch bone). 2. The Os 

 ischium , or Os st-dentariitm (sitting bone). 3. The Os 

 pubis. 4. The Os sacrum, or sacred bone. 5. The Os 

 coccygis (hucUle or tail-bone, the extremity of the spine). 

 6. The lumbar vertebrse, forming the base of the spinal 

 column. 7. The thigh bones. 



