Witson anp Martin—Rod-like Tactile Organs in the Muzzle of Ornithorhynchus. 191 
As noted by Meckel* the infra-orbital nerve bundles emerging from the 
foramen pass forwards, some dorsad, some ventrad, of the marginal cartilage to reach 
the respective surfaces of the upper lip. 
The abundant supply of bundles of medullated fibres is very great, and such as 
we have never seen in any other animal. Some idea of this extensive nerve supply 
may be gained by consulting fig. 12, Pl. vm., in Meckel’s monograph already referred 
to ; or our own fig. 1, Pl. xxiv., which represents a photo-micrograph of a transverse 
section of the extreme lateral edge of the flattened snout. . In this section, which was 
stained by Kultschitzky’s method,+ the transversely cut bundles of medullated nerves 
are seen lying midway between the cartilage and the surface, those on the upper 
surface being much larger than the inferior ones. The blue-black staining of the 
large bundles of medullated fibres strikingly demonstrates the extraordinary wealth 
of nerve tissue. 
In the Proceedings of the Physiological Society, June, 1884, Mr. Poulton gives 
a very brief account of some points in the structure of the skin covering the so-called 
beak of the Platypus.{ Among other things he mentions the existence of certain 
rods embedded in the epidermis and arranged perpendicularly to the surface, which 
he describes as hair-like in structure. This author also pomts out that at the base 
of each rod two or more Pacinian bodies are applied, with their axes parallel to the 
surface, and he considers that these latter are operated upon by pressure applied to 
the slight, boss-like projections of the rods at the surface, comparing them, in fact, 
to the knob of the push of an electric bell. 
Before we became acquainted with this brief note of Mr. Poulton’s observations, 
we had devoted a considerable amount of attention to the investigation of these 
structures, and had come to conclusions which are largely identical with his as 
regards their general structure and probable function. In our investigations, 
however, a number of additional structural points: have revealed themselves which 
represent a material extension of our knowledge of these peculiar sense organs. 
Our observations have been made upon longitudinal and transverse sections, 
including several series, of freshly fixed tissue, treated by very various ways of 
stainng. The most valuable for the purpose of tracing the destination of the many 
nerve-fibres which are supplied to each rod-like organ, we have found to be Freud’ss 
gold chloride, and Kultschitzky’s method.| 
* Loe. cit. 
+ Anat. Anzeiger, 1889, p. 223. 
t ‘On the tactile terminal organs and other structures in the bill of Ornithorhynchus.” Journ. Physiol. Vol. V. 
This paper is stated to be an abstract only, but we have been unable to discover any fuller contribution by Mr. Poulton. 
§ Arch. f. Anat. u. Physiol. 1884, p. 453. 
| Loe. cit. 
