190 



It was V. BiscHOFP who first enunciated this view in regard to 

 the true significance of the interosseus primus volaris ; and afterwards 

 I was able to confirm his results in every particular. But Professor 

 Flemming has not stated v. Bischofp's observations accurately. He 

 says: „Die Portion B zieht v. Bisciioff bei Aff"e und Mensch mit 

 Recht zum Adductor, motiviert aber nicht, weshalb dies nicht auch 

 mit G geschieht; er scheint es eben einfach als gegeben anzunehmen, 

 dass letzterer 'der tiefe Kopf des Flexor brevis' sein müsse." Now 

 V. Bischoff did not consider G to be the deep head of the flexor 

 brevis. Professor Fleminonci has evidently been misled by v. Bischoff's 

 figure^) in which the interosseus primus volaris is drawn forwards, 

 by a thread out of its natural position. In no part of his memoir 

 does V. Bischoff take notice of the slip 6', but in the text he re- 

 marks: „Der innere Kopf des Flexor pollicis brevis ist nämlich bei 

 dem Menschen sehr schwach und wie beim Orang und Hylobates ganz 

 durch den Adductor obliquus in die Tiefe gedrängt, so daß er erst 

 nach Entfernung desselben sichtbar wird. Er ist bisher entweder gar 

 nicht beachtet, oder von Dürsy und Henle unter der Bezeichnung 

 des Interosseus internus I oder pollicis et indicis beschrieben worden 2)." 



Professor Flemming also enters into the question of the nerve- 

 supply of the muscles of the thumb and although it has led him to 

 form a correct estimate of the homologies of i?, C and D, it cannot 

 be regarded as a safe test to apply in every instance; more especially 

 is this the case in the present instance, because wherever two nerves 

 approach each other and reach the confines of their distribution there 

 is a tendency to variation. Three years ago I met with an example of 

 this in the hand of a Negro (Fig. 1) which I had obtained from Sierra 

 Leone. In this I traced a twig from the median nerve under cover of the 

 tendon of the flexor longus pollicis into D (i. e. the adductor obliquus 

 of the hand). A short time afterwards a deviation of the reverse kind 

 came under my notice, in which a twig from the ulnar nerve, after sup- 

 plying B, sank into A (i. e. the radial head of the flexor brevis pollicis). 

 My assistant Dr. Beooks having independently observed similar va- 

 riations, was led to investigate the nerve-supply of the muscles of 

 the thumb more fully. His results, which are of a very interesting 

 character, were published in the Journal of Anatomy and Physiology 

 in July 1886. The following table taken from this article will suffice 

 to show that the nerve-supply in this locality cannot be regarded as 

 affording an infallible guide to the homologies of the muscles: 



1) Beiträge zur Anatomie des Hylobates leuciscus, Tab. V, Fig. 1 d. 



2) p. 20. 



