CHAP. vi.J SOME OTHER SENSATIONS. 269 



Pacinian corpuscle accordingly exhibits a series of concentric lines 

 separating spaces, the lines being especially close together near 

 the axis. Each space represents a capsule or coat of connective 

 tissue consisting of hardly more than fluid, traversed by transverse 

 and longitudinal fibres, and defined by a membrane both on its 

 inner and outer side. The lines in the section of a corpuscle re- 

 present the junctions of the inner membrane of one capsule with 

 the outer membrane of the one lying to its inside. They are really 

 the expression of lymphatic spaces, since each membrane of two 

 adjoining capsules is covered with a layer of flat lymphatic epithe- 

 lioid plates, the two layers leaving a linear space between them. 

 Frequently a blood-vessel entering into the corpuscle at the side 

 is distributed to the capsules, or at least to the outer ones. 



A single nerve-fibre approaches the base of the corpuscle and 

 as it draws near undergoes a great development of its sheath of 

 Henle, which becomes transformed into a series of concentric, or 

 in section parallel, sheets of connective tissue separated by lymph 

 spaces. After reaching the corpuscle, the several sheets of the 

 enlarged sheath of Henle leave the nerve fibre in succession to 

 become the capsules of the corpuscle ; and when the nerve fibre 

 penetrates to the bottom of the core it consists only of axis, 

 medulla, and neurilemma. The neurilemraa is lost, passing oft' 

 either to the innermost capsule or to the core itself ; the medulla 

 also disappears ; but the axis-cylinder is continued undivided up 

 the axis of the core to the far end where it ends in a blunt 

 somewhat swollen point, or more frequently dividing ends in a 

 number of such terminal knobs. Sometimes the nerve fibre 

 passes straight through the corpuscle without ending ; at the far 

 end of the core it regains its medulla and neurilemma, takes up in 

 turn the various capsules to form a thickened sheath of Henle, and 

 leaves the corpuscle much as it entered it. 



It is obvious that in the Pacinian corpuscle as in the more 

 minute end-bulb, we have to do with a special development of 

 connective tissue around an abruptly ending axis-cylinder. The 

 whole arrangement has the air of a mechanical device; but it 

 would be hazardous to insist too much on this. 



Pacinian corpuscles are found in abundance clustered round 

 the nerve branches running in the subcutaneous tissue of the 

 palmar surface of the hand and sole of the foot, especially in the 

 regions of the digits. It has been calculated that about 600 are 

 present in the under surface of each hand, and about as many in 

 each foot. ' They are much more sparse on, and often wholly 

 absent from, the nerves of the skin in the back of the hand and 

 foot, the upper arm and the neck. They occur on the nerves of 

 the mamma and of the genital organs. They are very numerous 

 along the nerves of the joints, especially in the flexures, about a 

 hundred being counted at the elbow ; they are also found along 

 the periosteal nerves of the shafts of some bones, and occur 



