SENSE-ORGANS OF THE INTEGUMENT. 169 



From the Reptilia onwards, so-called Pacinian corpuscles 

 are present in addition to the above-described tactile organs. They 

 undergo very numerous modifications, but each consists essentially 

 of numerous concentric lamellae (Fig. 139, Q, Z), enclosing the 

 termination of the axis-fibre with its protoplasmic sheath, which 

 dilates at the distal end into a sort of knob surrounded by a double 

 row of cells (Fig. 139, JK]. Thus the axis-fibre receives the 

 external impressions indirectly, that is, by means of the cells in- 

 vesting the knob-like end-organ. Organs of this kind are uni- 

 versally present in the skin of Mammals, and differ from the 

 tactile spots and tactile corpuscles in position: they 

 are found in the deeper layer of the derma, as well as in 

 the panniculus adiposus, the interstitial connective-tissue, and in 

 the various organs of the abdominal cavity (e.g. the mesentery, 

 mesocolon, pancreas, and portal fissure of the liver of the Cat), 

 the fascia3, tendons, vas deferens, periosteum, pericardium, pleura, 

 corpora cavernosum and spongiosum, the wing-membrane of 

 Bats, &c. 



These organs are not entirely wanting in any part of the skin 

 of Birds, but are particularly abundant on the beak, and at the 

 bases of the contour- wing- and tail-feathers. So-called corpuscles 

 of Grandry are also present in the beak. 



In all the tactile cells and tactile and Pacinian corpuscles we 

 have to do with organs of touch, or, expressed generally, with 

 means for the appreciation of sensations in the skin. 



It is impossible to say definitely which nerve-endings have to 

 do with the perception of temperature; it is not improbable 

 that the tactile cells, as well as the nerve-fibres with knob-like 

 swellings ending freely in the epidermis, are concerned in this 

 (Fig. 131, <7). 



BIBLIOGRAPHY. 



BEARD, J. On the Segmented Sense-organs, and on the Morphology of the Vertebrate 

 Auditory Organ. Zool. Anz. Nos. 161 and 162, 1884. On the Cranial Ganglia 

 and Segmental Sense-organs. Zool. Anz. No. 192, 1885. The System of Bran- 

 chial Sense-organs, and their Associated Ganglia in Ichthyopsida. Quart. Journ. 

 Micros. Science, 1885. 



GOLDSCHEIDER, A. Nc'iic Thatsaclien iib. die Hautsinnesnerven. Arch. f. Anat. u. 

 Physiol. 1885. 



KOLLIKER, A. Stiftchcnzellen in der Epidermis von Froschlarven. Zool. Anz. 1885. 



LEYDIG, F. Ueber die Sfhleimcandle der Knochenfische. Arch. f. Anat. u. Physiol. 

 1850. Ueber Organe eines sechsten Sinncs. Nova acta aead. Caes. Leopold. Carol. 

 Germ. nat. curios. Bd. XXXIV. 1868. Stiftchenzellen in der Oberhaut -von 

 Batrac.hicrlarvcn. Zool. Anz. No. 212, 1885. 



MALBRANC, M. Sinnesorgane der Seitenlinie bei Amphibien. Zcitsch. f. iviss. Zool. 

 Bd. XXVI. 1875. 



MERKEL, FR. Ueber die Endigungen der sensiblen Nerven in der Haut der Wirbcl- 

 thiere. Rostock, 1880. 



SCHULTZE, F. E. Ueber die becherform. Organe der Fische. Zeitsch. f. ivfss. Zool. 

 Bd. XII. 1863. Ueber die Sinnesorgane der Seitenlinie bei Fischcn und 

 Amphibien. Arch. f. mikr, Anat. Bd. VI. 1870. 



SCHWALBE, G. Lehrb. der Anatomic der Sinnesorgane. Erlangen, 1883. 



SOLGER, B. Seitenorgane der Fische. Arch. f. mikr. Anat. Bd. XVII. und 

 XVIII. 



