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



The drawings forming the accompanying Plates are from nature, and in all cases 

 enlargements. By their representation side by side in series a much better idea of the 

 family and generic distinctions are obtained than by mere verbal descriptions. Indeed 

 the latter have grown inordinately in my hands ; and but for the circumstance that the 

 full data whereon my conclusions are founded are absolutely necessary, pending the fact 

 of this series of ossicula being unique, or certainly the most extensive now extant, 

 I should gladly have dispensed with this portion of the labour, and curtailed my text 

 accordingly. 



In the Journal of this Society (Zool. No. 68, vol. xiii. p. 185) and in the Proc. Roy. 

 Soc. (No. 172, vol. xxv. p. 101) I have already indicated briefly a few of my results, and 

 in the latter referred to those gentlemen to whom I have been indebted for objects, 

 advice, and assistance. 



The Auditory Ossicles in Man. 

 The Malleus. — In the human malleus (PL LVIII. figs. 1 & 2, taken from a fully 

 developed fcetus) the portion of the head above the articular surface is prominent, 

 smooth, and convex, projects more on the outer than the inner side, and is broadest 

 in its lateral measurement. Posteriorly it bears the articular surface for the incus, 

 which has very elevated borders and is about three times as broad as it is deep vertically. 

 This surface lies very obliquely compared with the mallei of most mammals, so that 

 its external extremity is much higher than its internal. It is generally described 

 as " saddle-shaped," though, from a functional point of view, Helmholtz t has objected 

 to this expression. In most works on human anatomy it is regarded as if it were one 

 single facet; but on comparing it with the same surface on the malleus of a Cat 

 (PL LVIII. figs. 30 & 31), it will be seen that it should be considered as made up of two 

 facets, much less distinct, it is true, than in Felis and most other mammals, but far 

 better-marked than in certain monkeys. A very faint groove, more marked in some 

 human mallei than in others, and not reaching either extremity, divides them, running 

 in the very oblique long axis of the whole surface. The more internal and upper facet 

 (PL LVIII. fig. 30, a * a), or portion of the articular surface above the groove, repre- 

 sents that facet which is almost completely superior in position in most lower mammals 

 (fig. SI, a* a), the more external (b * b) below this groove corresponding to the lower 

 facet in many other mammals. Both rise into a high vertical convexity about the 

 middle of the whole surface, which is there much contracted ; their planes slope down- 

 wards towards the groove, so that a concavity is formed, plainly visible when the arti- 

 cular surface is viewed sideways. Now it may be remarked that of all the portions of 

 the three ossicula there is none that requires so minute and careful an investigation as 

 the articular surface of the malleus ; and although the results of such labour are often 

 puzzling, and not invariably satisfactory, still, as a whole, many distinctive points of 

 value will be found in this region among the different orders of mammals. It will be 

 shown, when speaking of the ruminants, that the characters of this surface undergo 



t See his remarks on the malleo-incudal articulation in his work, ' The Mechanism of the Ossicles and the 

 Membrana Tympani,' translated by J. Hinton, New Sydenham Society, 1874. 



