452 



11. The second class of muscular varieties comprises those instances 

 in which we find normal muscles multiplied by simple reduplication, 

 the double portions either being placed in different planes, or in diffe- 

 rent vertical positions. The former arrangement I have found to be 

 rather the more frequent, and it has occurred, in my experience, to 

 several muscles. We must, however, be careful to distinguish abnor- 

 malities of this class from those of the fifth group, with which they are 

 liable to be confounded ; the main distinction being that, whereas in 

 every example of this class all or some of the portions of the varying mus- 

 cles are doubled, in the fifth subdivision, on the other hand, each part 

 is but single, although severed from those others with which it normally 

 should be united. 



1. The rhomboideus major I found to be the seat of a partial variety 

 of this class, on the left side of a female subject. It was almost com- 

 pletely split into two planes of fibres, especially along its lower border. 

 At the upper edge of the muscle the fibres of the different planes 

 coalesced more or less distinctly. 



2. The pectoralis major has been on several occasions partially cleft 

 into two planes, more or less distinctly, and in one case was perfectly 

 severed. This arrangement occurs in the horse, sheep, and dog. 



3. The sterno- thyroid was double on the left side of a strong male 

 subject, the two portions lying parallel ; and (4) on the same side of 

 this subject there was a double levator anguli scapulae. 



5. In the right forearm of a thin female subject the supinator longus 

 was double for the largest part of its extent, while the same variety was 

 presented in a corresponding extremity in the case of the (5) palmaris 

 longus. The double arrangement of the former muscle occurs, according 

 to Meckel, in the three-toed sloth, and in the anteater ; it is likewise 

 cleft in the seal. 



7. The abductor pollicis brevis manus I found presenting this ano- 

 maly — the two muscles lying parallel, and separated by a cellular 

 interval. This state was described by Sommering, who believes it to 

 be the normal arrangement of the muscle. 



8. The rectus capitis lateralis, and (9) rectus capitis posticus major 

 and minor, were each in at least one instance found double. 



1 0. The extensor ossis metacarpi pollicis I have seen in several in- 

 stances presenting this irregularity : in one case three parallel muscles 

 and tendons existed ; in another the muscle at first was single, but ended 

 below in two bellies, which were inserted by tendons quite separate and 

 distinct from each other, the inner of which overlapped the outer 

 (11). The same varieties I have seen to occur in the case of the extensor 

 secundi internodii pollicis. 



12. The extensor minimi digiti I have likewise seen entirely doubled. 

 Usually, however, when this condition occurs, the tendons and bellies of 

 the two muscles separated except for about an inch or so from the 

 origin, and by no means unfrequently a single belly existed, from which 

 two tendons were detached, both of which were distributed to the little 



