T R I 



linea afpera. It arifes, principally by flefhy fibres, from 

 the anterior furface of the body and ramus of the pubes ; 

 it paflTes obliquely downwards and outwards, with a little 

 obhquity backwards, becoming broader and thinner, and 

 having an attachment of about three inches to the hnea 

 afpera, from the little trochanter downwards. Here it is 

 clofely connefted to the two other adduftors, and to the 

 peftinalis. The perforating arteries go through its fibres. 

 The peftinalis and adduftor longus cover it in front ; the 

 adduftor magnus behind. The inner edge is partly covered 

 by the gracilis, partly concealed between the firil and third 

 adduftors : the outer correfponds to the obturator externus 

 and the tendon of the pfoas magnus. 



The adduftor magnus or tertius, or the great head, is a 

 broad and thick mafs, flattened, nearly triangular, placed at 

 the infide of tlie thigh, where it readies from the ifchium to 

 the whole length of the linea afpera, and to the tubercle of 

 the internal condyle. It arifes, by a ilrong aponeurofis and 

 by fleihy fibres, from the external furface, and from 

 the margin of the ramus and tuberofity of the ifchium. 

 From this point the mufcnlar fibres fpread out into a great 

 breadth, and take very different dircftions ; the fuperior 

 going nearly tranfverfely, the middle obliquely, and the in- 

 ferior almoft perpendicularly downwards. The general di- 

 reftion of the mufcle is from above downwards, and from 

 within outwards. Its attachment begins at the upper end of 

 the hnea afpera, juft below that of the quadratus : it is fixed 

 to the whole length of that line, being connefted to the two 

 preceding mufcles. When the linea afpera bifurcates at its 

 termination, the adduftor magnus divides into two portions ; 

 an external or pofterior, which ends in a point between the 

 vaftus internus and the fliort head of the biceps ; and an in- 

 ternal or anterior, which is connefted to the edge of the 

 vaftus, and defcends with it to the internal condyle. Thefe 

 two portions have between them an interval, occupied by the 

 femoral artery and vein : this interval is covered in front 

 bv an aponeurofis, extended from the adduftor to the tri- 

 ceps, and palling over the femoral artery. There are other 

 openings in the aponeurofis for the pafTage of the perforating 

 arteries. The adduftor magnus is fixed to the Hnea afpera 

 by Ihort aponeurofes ; and to the tubercle of the internal 

 condyle by a ilrong tendon, which is expanded above into a 

 broad aponeurofis. The mufcular fibres pafs between the 

 tendon and aponeurofes, which fix the mufcle to the iichium, 

 and thofe which are connefted to the femur. The internal 

 fibres are very long, and direfted obliquely downwards and 

 outwards : the middle ones are Ihorter, and direfted more 

 outwards, and the external or upper are the fiiorteft, and 

 nearly tranfverfe. 



The firft and fecond adduftors, the fartorius, and the 

 crural artery, cover it in front : the femi-tendinofus, femi- 

 membranofus, biceps, gluteus magnus, and fciatic nerve, 

 cover it behind. The inner edge is covered by the gracilis, 

 fartorius, and fafcia : the outer edge is the infertion in the 

 hnea afpera. The upper margin, or the bafe of the tri- 

 angle, is parallel and clofe to the under edge of the qua- 

 dratus ; the lovrer extremity, or apex, is the tendinous 

 attachment to the condyle. 



The triceps will move the thigh in the direftion of adduc- 

 tion, or towards the oppofite limb : it will carry one thigh 

 acrofs the other, as in fitting crofs-kneed: it will prefs the 

 thighs againft any thing between them, as the fides of the 

 horfe in riding. The firft and fecond heads will bend the 

 hip : the third will extend it, when it has been previoully 

 bent. All three will rotate the thigh outwards. By draw- 

 ing the thighs inwards, the triceps mufcles keep them per- 

 pendicularly under the pelvis, fo that they fupport it, and 



T E I 



through it the whole upper parts of the body. When we 



ftand on one leg, the triceps will regulate the degree of in- 

 clination of the pelvis over the thigh, and prevent it from 

 falling over on that fide. 



Triceps extenfor cubili, (triceps brachialis ; anconeua 

 longus, externus, and internus, Winflow ; fcapulo-humero- 

 olecranien,) a large thick mufcle, of an elongated figure, co- 

 vering the back of the arm, and extending from the fcapula 

 and humerus to the olecranon. Its long head arifes frem the 

 inferior edge of the fcapula, juft below the glenoid cavity, 

 by a flat tendon, about three-quarters of an inch broad : the 

 fecond or external head commences, in a pointed form, from 

 the back of the humerus, a little below its head ; and the 

 third, internal, or fliorteft head, begins on the inner and pof- 

 terior part of the humerus, an inch below the fecond. The 

 two latter are feparated from each other by an interval, in 

 which the profunda humeri major artery runs, accompanied 

 by the radial or mufcular fpiral nerve : this veflel and nerve 

 continue their courfe, from the inner to the outer fides of 

 the limb, between the mufcle and the bone. Below the 

 points mentioned already, as the origins of the fecond and 

 third heads, thefe portions arife by fleihy fibres from the 

 whole pofterior furface of the humerus, except where the 

 radial nerve and the profunda humeri pafs, and from the 

 inter-mufcular aponeurofes fixed to the lateral ridges of the 

 bone. The long or middle head continues diftinft from the 

 others for fome difl:ance, paffes behind the fliouldcr-joint, 

 between the teres major and minor mufcles, and in front of 

 the latiflimus dorfi ; it then foon joins the two others. It 

 is firft thin and flattened ; then increafes in fize. The two 

 other heads are pointed and thin above, and increafe gra- 

 dually : they all then join about the middle of the humerus, 

 which is the thickeft part of the mufcle ; for below it again 

 decreafes. From the aponeurofis of the middle head, and 

 from the back of the humerus, the fibres are continued 

 obliquely downwards and backwards into a broad and flat 

 tendon, which covers the lower and pofterior part of the 

 mufcle, becomes narrower and thicker as it defcends, paffes 

 behind the elbow-joint, clofely adhering to its fynovial 

 membrane, and is inferted into the upper and pofterior 

 rough extremity of the olecranon. Several fibres are de- 

 tached from it to the fafcia of the fore-arm, and par- 

 ticulariy to that part of the fafcia which covers the 

 anconjeus. 



The pofterior furface of this mufcle is convex ; covered 

 above by the teres minor and deltoid, and in the reft of its 

 extent, merely by the fafcia and fltin. The anterior furface 

 is in contaft above with the fubfcapularis, teres major, and 

 latiflimus dorfi ; with the whole back of the humerus ; and 

 with the fynovial membrane at the back of the elbow. The 

 outer edge is fixed to the external ridge of the bone, and 

 to the external intermufcular aponeurofis, the att.ichmeiit 

 being interrupted only at the pafTage of the radial nerve. 

 The internal edge is fixed to the correfpouding parts on the 

 infide : the ulnar nerve lies on it. The upper extremity is 

 divided into three portions, forming the three heads already 

 defcribed : the lower extremity is fingle. 



The triceps extends the elbow-joint, by moving either the 

 bones of the fore-arm on the arm, or vice -verfd. Its long 

 head may carry the arm backwards. 



Triceps, in Mythology, a furname given to Mercury, be- 

 caufe he exercifes his funftions in heaven, on earth, and m 

 the infernal regions, and is exhibited under three differcftt 

 forms, according to the three different places in which he 13 

 employed. 



TRICERA, in Botany, from Tfii;, three, and ■<(;«<, a 

 horn, becaufe of the tliree horns, originating in the perma- 

 nent 



