98 THE VOYAGE OF H.M.S. CHALLENGER. 



In the suspensory ligament of the Ox there is a large amount of muscular tissue, not 

 only on its surface but also embedded in its interior. On the lower half of its super- 

 ficial surface we find a thick layer of fleshy fibres. This is even continued down for some 

 distance upon the slips into which the ligament divides. But it is upon the deep 

 surface of the suspensory ligament that we observe the greatest quantity of muscular 

 tissue. Here it extends from the origin of the structure down to the point where it sub- 

 divides, and it is disposed in three parallel and longitudinal strands; of these (1) one 

 passes down to the angle of divergence of the two slips for the sesamoids of the medius, 

 (2) another to the angle of divergence of the slips for the sesamoids of the annularis, 

 whilst (3) the third is carried downwards between the two preceding to the central slip, 

 and this is much the most strongly marked ; indeed, at the lower part of the ligament, 

 it extends right through the structure to its posterior or superficial surface. Each strand 

 consists of short fibres arranged in an irregularly bipenniform manner. 



When thin transverse microscopic sections of this ligament are made, the muscular 

 tissue is seen to penetrate deeply into its substance. It is arranged in the form of four 

 small circles or rings, with thick outlines placed side by side, nearer the anterior than 

 the posterior surface of the structure (PI. XL figs. 8 and 8a.) It is present in much larger 

 quantity than in the case of the Horse. When examined under the microscope these 

 transverse sections show a considerable number of fat cells associated with the muscular 

 fibres, and amidst these transversely cut nerves and blood-vessels. 



But we must endeavour to determine the intrinsic muscle or muscles from which 

 the suspensory ligament of the Ox is derived. In this we are aided by the definite 

 arrangement of the muscular fibres. In the Horse only one muscle, viz., the flexor 

 brevis medii, enters into its formation ; in the Ox we have clear proof of at least two 

 muscles. Each muscular ring seen in the substance of the transversely divided ligament 

 represents the head of a flexor brevis. The ligament is thus formed by the union and 

 fibrous degeneration of both heads of the flexor brevis medii, and of the flexor brevis 

 annularis. The central slip of attachment which passes forwards between the digits, 

 simply represents a portion of the outer head of the flexor brevis medii, and of the inner 

 head of the flexor brevis annularis, proceeding to obtain an insertion into the extensor 

 tendons. 



No evidence exists to show that any of the other intrinsic muscles which usually 

 belong to the medius and annularis are contained in this ligament. 



But it may be asked, what do those tendinous cords which join the tendons of the 

 perforatus homologate ? Are they adductors, or indeed have they any muscular origin at 

 all ? I feel confident that they have not. Even before they separate from the ligament 

 they have an appearance as if they hardly belonged to it, but constitute a thick layer 

 on its superficial surface distinct from, although united to the body of the structure. I 

 believe that they are derivations from the dense fascia, which invariably covers the 



