On the distribution of the cutaneous nerves etc. 305 



of the middle finger; he notices that in rare cases this nerve may 

 supply the fourth or even the fifth finger x ). Quain states that the 

 radial nerve supplies the dorsum of the thumb, the index and the 

 radial border of the middle finger ; the ulnar nerve on the other hand 

 is distributed to the little finger and to the ulnar border of the ring 

 finger; while the adjacent sides of the middle and ring fingers receive 

 their nerve-supply from combined twigs of the radial and ulnar nerves 2 ). 

 I have already referred to the able paper by Dr. R. Jacobi which 

 appeared in the „Berliner klinische Wochenschrift" last year. This ob- 

 server suffered in his own person the accident of section of the median 

 and the musculo -spiral nerves. His observations led him to the con- 

 clusion that a „collateral" (double or multiple) innervation of the skin 

 existed which would account for the clinical phenomena. I regret that 

 I have not had the opportunity of consulting his larger work on the 

 „Collateral Innervation of the Skin" 3 ), but, from what I can gather 

 from the paper I have read, he appears not to have made any ana- 

 tomical researches with a view of demonstrating the collateral inner- 

 vation of the skin. He mentions, however, the following interesting 

 observation, that if one of the four nerves which supply any of the 

 toes is cut and a portion of the peripheral stump subjected to micro- 

 scopical examination some weeks after the section, a certain number 

 of perfectly intact fibres will be found lying among the degenerated 

 fibres. This gives evidence, not of a true double innervation of the 

 skin, but offers an example of „nerves without ends" as described by 

 Hyrtl. Such communications are well known to occur abundantly on 

 the dorsum of the hand and fingers and are of the nature of the 

 „anastomoses" on which Létiévant throws so much weight in the ex- 

 planation of the clinical phenomena. 



*) Op. cit. Dritter Band. p. 209. „N. radialis superficialis. Liefert selten auch 

 Nn. digitales dorsales für den vierten Finger, oder (sehr selten) zugleich für den 

 fünften Finger, während der N. ulnaris dorsalis fehlt". In Dr. Hepburn's paper 

 (above referred to) a case is recorded in which the dorsal branch of the ulnar nerve 

 was absent. — „Here the radial nerve supplied the cutaneous branches for the entire 

 dorsum of the hand and fingers". He also describes a case in which the radial nerve 

 was wanting, the dorsum of the hand being supplied by the ulnar and musculo- 

 cutaneous nerves. 



2 ) Quain's Anatomy. Ninth Edition. 1882. Vol. I. p. 610 and 616. 



8 ) Archiv für Psychiatrie u. Nervenkrankh. Bd. XV. S. 151—183 u. 506—559. 



Internationale Monatsschrift für Anat. u. Phys. V. 20 



