Situated on the internal surface of the arm, it arises from the external aspect of the tendon of the latissimus dorsi; it is very highly developed in the horse, in which it also arises from the posterior border (axillary) of the scapula; then, covering in part the internal head of the triceps and also the long portion, on the superior border of which it is folded, it proceeds to be inserted into the olecranon process and the anti-brachial aponeurosis. It extends the forearm on the arm. Further, it makes tense the aponeurosis into which it is inserted; this explains the name of _tensor of the fascia of the forearm_, which is sometimes given to it. It seems to us interesting to add that, abnormally, we sometimes find in man an analogue of this muscle. It is given off from the latissimus dorsi, near the insertion of the latter into the humerus; it accompanies the long head of the triceps and becomes fused with it. Sometimes it is inserted into the olecranon process, at other times into the antibrachial aponeurosis or the epitrochlea. It is on account of its insertion into the last-mentioned, in some cases, that it is also designated by the name of _dorso-epitrochlear_ muscle.[25] [25] L. Testut, 'Anomalies musculaires chez l'homme expliquées par l'anatomie comparée,' Paris, 1884, p. 118. A. F. Le Double, 'Traité des variations du système musculaire de l'homme et de leur signification au point de vue de l'anthropologie zoologique,' Paris, 1897, t. i., p. 203. Édouard Cuyer, 'Anomalies musculaires' (_Bulletins de la Société Anthropologique_, Paris, 1893). Muscles of the Forearm Before commencing the special examination of each of the muscles of this region, it is absolutely indispensable to consider their general arrangement, and to determine very clearly how we should study them. We are too well convinced of the importance of this preliminary examination to dismiss it without entering rather fully into it. Indeed, the region on the myological study of which we are now entering is, unquestionably, one of the most complicated with which we have to deal. We know besides, in regard to the study of the forearm in man, how much a definite method is necessary in order that the arrangement of the muscles of this region be fixed in the memory, and that we are unable to obtain this result otherwise than by grouping the twenty muscles which constitute it in clearly defined regions. We also know that these muscles are first studied with the forearm in the position of supination, and that it is only when they are well known after having considered them in this position that we are able to analyze and comprehend their forms when it is in pronation.