MUSCLES OF THE FORE-ARM. 



365 



sion. Unless the surgeon can distinctly feel 

 the head of the radius, so that he can clearly 

 ascertain on rotating the lower portion with the 

 hand, that the upper does follow but remains 

 perfectly unmoved, he has ncsequivocal guide 

 as to the real nature of the injury. 



If the ulna is fractured separately from the 

 radius, which seldom occurs, the injury gene- 

 rally happens to the lower third of the bone, 

 which is much smaller and more exposed than 

 the upper ; the accident is easily detected by 

 running the finger down the posterior edge of 

 the bone. When the radius is fractured near 

 its centre, the pronator quadratus muscle ob- 

 tains entire power over the bone, and drawing 

 the lower portion across towards the ulna, 

 causes a considerable projection in the anterior 

 interosseous space. If this be not corrected by 

 the use of a pad, as recommended a little fur- 

 ther on, the two bones will unite, and all mo- 

 tion of pronation and supination be entirely 

 lost. 



In all these cases of fracture of the bones of 

 the fore-arm, nearly the same plan of treatment 

 is required, namely, 1st, two pads, increasing in 

 thickness from the elbow to the wrist, and not 

 wider in any place than the arm itself, suffi- 

 ciently soft to be pushed well into the interos- 

 seal spaces, applied anteriorly and posteriorly ; 

 a long linen roller enveloping the hand and the 

 whole of the fore-arm, and pressing the pads 

 between the two bones, so as to counteract the 

 action of the two pronator muscles which have 

 a tendency to bring them together. Splints ex- 

 tending from the elbow to the hand. 



When the radius alone is fractured, it is ad- 

 visable not to support the hand, but to allow it 

 to hang down, and by this plan the hand acting 

 as a weight, will draw the lower fractured por- 

 tion, which has a tendency to overlap the 

 upper, downwards, and thus bring them into 

 apposition. 



(Samuel Solly.) 



FORE-ARM, MUSCLES OF THE. 



When we consider how varied and complex are 

 the motions of the arm and hand, it is no matter 

 of surprize that so many as nineteen muscles 

 should be found composing the fleshy mass of 

 the fore-arm. 



These muscles may be classified in reference 

 to their action, and are briefly enumerated as 

 follows: 



In the first place there is one muscle physio- 

 logically belonging to the upper arm, the anco- 

 neus; the rest are connected with the hand; 

 for instance, there are three flexors of the hand; 

 flexor carpi radialis, flexor carpi ulnaris, pal- 

 mar is longus. Three extensors of the hand, 

 extensor carpi radialis longior, extensor carpi 

 radialis brevior, extensor carpi ulnaris. Three 

 long flexors of the thumb and fingers ; flexor 

 communis digitorum sublimis, flexor communis 

 digitorum prqf'undus, flexor longus proprius 

 pollicis. Five extensors of the thumb and 

 fingers, extensor ossis metacarpi pollicis, exten- 

 sor primi internodii, extensor secundi internodii, 

 extensor communis digitorum, extensor indicis. 



Two supinators, supinator radii longus, supina- 

 tor radii brevis. Two pronators, pronator ra- 

 dii feres, pronator quadratus. 



In proceeding to describe the attachments 

 and relations of the foregoing muscles, it will 

 be found convenient to examine them as they 

 are met with in the following regions of the 

 fore-arm. 1. The anterior region, which con- 

 tains a superficial and a deep set of muscles. 

 2. The posterior region, which likewise has its 

 superficial and its deep layers of muscles. 

 These regions again may be conveniently sub- 

 divided into radial and ulnar sections, between 

 which a very natural line of demarcation is 

 observable after the skin and adipose tissue 

 have been removed. 



Exactly on this line, and one-thiid from the 

 elbow and two-thirds from the wrist-joint, two 

 long muscles will be found in contact, the supi- 

 nator radii longus in the radial section, the 

 flexor carpi radialis in the ulnar. Above and 

 below this point these muscles diverge. The 

 flexor carpi radialis, at its origin from the inter- 

 nal condyle, is distant, from the boundary line 

 referred to, at least one-third of the transverse 

 diameter of the arm, and the space thus left, 

 triangular in its figure, contains a large portion 

 of the pronator radii teres. The radial edge of 

 the pronator radii teres is in contact with the 

 supinator radii longus to the extent of about 

 an inch and a half; this muscle descending in 

 like manner obliquely from its origin in the 

 ulnar section towards the radial leaves above a 

 similar though small triangular space, in which 

 the tendon of the biceps flexor cubiti is lodged. 

 Below the point referred to above, between the 

 elbow and wrist, the flexor carpi radialis runs 

 in contact with and on the ulnar side of the 

 boundary line till within an inch and a half of 

 the wrist-joint, where it gradually slides into 

 the radial section, so that at the annular liga- 

 ment the tendon of the flexor carpi radialis 

 will be found entirely in the radial region with 

 its internal edge in contact with the boundary 

 line. 



Thus it will be seen that a line drawn from 

 the elbow to the wrist and dividing the fore- 

 arm into two portions, of which the internal 

 or ulnar section is exactly two-thirds, while the 

 external or radial section is only one-third of 

 the transverse width, not merely forms an arti- 

 ficial division into radial and ulnar sections, 

 but also points out the exact situation of the 

 tendon of the biceps, the outer edge of the 

 pronator radii teres, and the flexor carpi radi- 

 alis, and in addition, as we shall presently see, 

 the supinator radii longus. The fleshy belly 

 of this muscle lies exactly parallel with this 

 boundary line in the upper half of the arm. 



In consequence of the supinator radii longus 

 becoming tendinous about the middle of the 

 fore-arm, and the tendon being narrower in its 

 transverse diameter than the muscle, a space is 

 left at the lower part of the arm between it and 

 the flexor carpi radialis, and the supinator radii 

 longus is no longer met in contact with the 

 boundary line. In this space is lodged the 

 radial artery, lying midway between these two 



