On the structure and development of the skull of the common frog (Rana temporaria, L.) / by William Kitchen Parker.

  • William Kitchen Parker
Date:
[1871]
Catalogue details

Licence: Public Domain Mark

Credit: On the structure and development of the skull of the common frog (Rana temporaria, L.) / by William Kitchen Parker. Source: Wellcome Collection.

Provider: This material has been provided by UCL Library Services. The original may be consulted at UCL (University College London)

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    nerve (8j; below the two bony masses is the huge deep fossa for the stapedial and inter- stapedial cartilages (st., it.st.); and below this hollow is the rounded unossified opisthotic region {op.), to which the stylo-hyal (sf.h.) has at last become closely attached. The broad occipital condyle (o.c.) is capped with persistent cartilage; and the exoccipital bony mass mounts up above the condyle into the supraoccipital region, and descends below into the base of the skull. The endoskeletal part of the premaxillary region has been described with the nose- capsule ; we now come to the lateral regions. There has been no tendency to segmentation of the superpalatal bar from the prefrontal mass (Plate IX. figs. 6, 7, s.pa., jpr.f.); and the prepalatal [p.])a.) is now a fiat triangular projection slightly afiected by endostosis, continuous with that of the rest of the bar. The constriction between the postpalatal and pterygoid regions is now obliterated [jit.pa.,]).g.); the ectosteal palatal lamina (fig. 7) has not increased in size relatively; thus most of the palatal region is left unarmed with bony matter. The subocular fenestra (s.o.f.) is a large ellipsoidal space made slightly reniform by the bulging of the cranial side-wall; outside it is bounded by the elegantly arcuate anterior part of the pterygoid (^^.). There is still a very solid core of hyaline cartilage to the pterygoid, the Anoura being very remarkable in that the ectosteal plates show, for the most part, so feeble an affinity for the cartilage within, and even for the endosteal bone into which the carti- lage is changed (' Shoulder-girdle and Sternum,' pis. 5-8, pp. 66-89). This unchanged core is most exposed on the upper surface (Plate IX. fig. 6). The metapterygoid bony spur {ni.pg.) is now small and placed anterior to the triangular infrahyomandibular (i.h.m.); behind the latter is the deep recess which bounds the Eustachian tube; and then the pterygoid grows downwards, backwards, and outwards, strongly clamping the suspensorium (figs. 1-7); this posterior portion of the ectosteal pterygoid is a siiper- erogatory growth of fibrous bone, its proper cartilaginous axis ending at the front margin of the suspensorium. The posterior part of the bony pterygoid is best seen from behind (fig. 4,2).g.), in which view we can most readily understand the manner in which the suspensorium is continuous with the skull in its metapterygoid or antero-external portion, and how it glides on the skull by its postero-internal portion, the infrahyomandibular (in.j}g., iJim.). The metapterygoid portion of the suspensorium is overhung by an eave of cartilage from the projecting periotic capsule; this eave is cut through in front of the suspensorium in the section (Plate X. fig. 8); and under the shadow of this eave the extrastapedial spatula ivLXws forwards to receive, on its outer surface, the fibres of the membrana tym- pani (Plate IX. fig. 3, a.t., e.st.). The cartilaginous eave is tiled over by the embracing supratemporal part of the squamosal, the projecting edge of which forms a strong ridge for the attachment of the ends of the cartilaginous annulus, which have now met each other (Plate IX. fig. 3, a.t., s.t.). The quadrate angle of the subocular arch now projects almost as much backwards as
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