374 MR. A. H. G. DORAN ON THE MORPHOLOGY 



unaware of this fact, has frequently searched in vain along the Glaserian fissure for this 

 process supposed to have been broken off. It forms with the neck an angle of 125°, and 

 runs almost horizontally forwards to the fissure. It is generally bowed regularly, and 

 is concave forwards ; sometimes it is somewhat wavy ; but in all cases the degree of cur- 

 vature is slight. When well preserved, the processus gracilis at birth is longer than the 

 manubrium. 



Below and internal to the processus gracilis the insertion of the tensor tympani muscle 

 is sometimes marked by a faint elevation, close to or upon the manubrium representing 

 the " processus muscularis " of Hyrtl, which attains a great development in some lower 

 animals. In the human malleus, however, an elevation is occasionally seen as marked 

 as its homologue in the Bears, presently to be described. 



That important process the manubrium, or handle, now claims our attention. In 

 Homo it is below the average length, far shorter than in ruminants or terrestrial Car- 

 nivora, though longer than in some Seals or Whales. It forms with the neck an angle of 

 about 140° ; Hyrtl gives 150°; but he must have taken the axis, not of the upper and greater 

 part of the manubrium, bat of the recurved portion at the tip, from strongly curved 

 examples. It is of a stout make, and broader at the base than in the Simiidse ; it is 

 much flattened laterally, the sides looking respectively antero-superiorly or postero- 

 inferiorly ; they are slightly convex, notwithstanding their compression. The extremity 

 is always slightly recurved, though more in some specimens than in others, and per- 

 ceptibly spatulate and smooth towards the tympanic membrane. The edges of the 

 manubrium are both thick and blunt ; and the outer edge, though of a certain breadth, 

 and giving attachment to fibres along its entire length, is rarely separated from each side 

 by sharply defined borders, so as to constitute a true and distinct outer surface, as seen 

 in many lower animals, and particularly in the Canidse *. This edge ends below in the 

 spatulate dilatation, above in a very distinct sharp projection, well curved outwards. 

 This is the " processus brevis :" its good development is a prominent feature in the 

 human malleus ; and it will be seen to be better marked in the higher than in the lower 

 Quadrumana, though it occasionally reappears in the latter. In most mammals it is 

 merely an angle at the outer aspect of the base of the manubrium ; in many it does not 

 exist even in that form, especially where the neck of the malleus is very short. 



Such is the human malleus. It may be seen as a good central type of the bone in 

 mammals, a type which very frequently reappears as we go downwards in the scale — a 

 malleus characterized by a well-developedjiead, a moderately long, constricted neck, and 

 a broad-based, stout manubrium. It holds an intermediate position between the almost 

 or quite neckless type seen in the Cebidse, in Tupaia, and in the true Squirrels, and the 

 broadly laminated form so well seen in the terrestrial Oarnivora and the artiodactylate 

 Ungulata. It will be seen to be repeated, with modifications, in the higher monkeys, re- 

 appearing among Carnivora in the Ichneumons, and certainly approached (with some 

 important distinctions) in the Seals. It is also imitated in some of the Insectivora, 



* In a recent contribution to the ' Archiv fur Ohrenheilkunde,' Trautmann describes and figures this condition as 

 if constant in Homo. It is only in a very few specimens of the human malleus, however, that I have distinguished 

 two distinct borders running completely from the processus brevis to the tip. 



