CITTANEOTJS NERTE-TERMTJiTATIONS TN MAMMALS. 5(59 



the inner circle are (with the exception of the slight curve near 

 the centre) perfectly straight until they become narrow near their 

 ends. These two points are of importance in showing that the 

 three divisions of fibres are anatomically difierent from each other, 

 a question to be taken into consideration in afterwards establishing 

 homologies. 



The fibrils of the inner circle can generally be traced as pro- 

 ceeding from the medullated nerves which pass to the organ. 

 These medullated nerves are generally from four to six in number, 

 and on arriving at the lower surface of the epidermic downgrowth 

 of the organ they divide into two or three branches, which are 

 the fibrils of the inner circle. We have never yet been able to 

 trace any connexion between the medullated nerves on the one 

 hand, and either the centre or outer circle groups of fibrils on 

 the other. What may be called the epidermic matrix of the 

 organ stretches down beyond the general level of the lower sur- 

 face of the epidermis as a bell-shaped projection, having the 

 appearance as if a mass of epidermic cells in the form of a bicon- 

 vex lens had been attached by one of its sides to the lower surface 

 of the epidermis ; and the medullated nerves pass to the lower 

 or free surface of this lens-shaped body, where they break up into 

 their ultimate fibrils, which enter the epidermis from that lower 

 surface of the lens-shaped mass. Below the same surface of the 

 mass, one or two small Pacinian bodies may be seen, which appear 

 to have no homology with any part of the nerve-apparatus on 

 hairs, are indeed without any representative in the noses of other 

 mammals, although they are plentiful in the beaks of birds ; and 

 therefore it will be unnecessary for us to refer to them again*. 

 The medullated nerves seldom approach the organ in the line of 

 its axis, but form an intricate plexus beneath the epidermis ; and 

 from this plexus nerves are given ofi" at opposite points, which 

 approach the base of the organ from the sides, and meet below 

 the epidermic downgrowth, where they suddenly take a turn at 

 right angles to divide and enter the epidermic downgrowth. 



Ganglion- Cells and Group of Central Nerve-jibrils. — Amongst 

 the epidermic cells forming the lens-shaped downgrowth, Mojsi- 



* Since writing the above, we have found reasons for considering that these 

 Pacinian bodies are the representatives of one or more forked tactile nerve- 

 endings which have not entered the epidermis and have become covered with 

 connective tissue, like the cut ends of the nerves in an amputated stump. This 

 gives the clue to the origin and function of the large Pacinian bodies in Man 

 and in the Cat tribe. 



