SENSE OF TOUCH IN ANIMALS. 371 



But in the greater number of Mammalia, the lips and the end of the nose 

 are the special seats of touch, many, as the ant-eaters, mole, hog, tapir, and 

 elephant, being provided with a movable snout. In the rhinoceros there is a 

 soft, hook-like expansion of the upper lip, which is constantly kept moistened, 



ly to that of the human hand. The skin of the zoopha^ 

 is very remarkable for the thickness and density of its structure. The true 

 skin consists of a thick, dense, whitish, opaque, fibro-cellular layer, provided 

 with innumerable elongated papillae, which enter into corresponding depres- 

 sions on the under surface of the thick black epidermoid layer. These papillae 

 are half an inch or more in length, and are said to be supplied with nerves as 

 well as vessels. It has been supposed by many familiar with the habits of the 

 whale, that the sense of touch is very acute in these animals, especially for un- 

 dulations transmitted through the water ; and that, in this way, the whales 

 can communicate with each other when alarmed. In Mammalia, the soft, 

 movable, papillated tongue is undoubtedly used as a tactile organ. 



The general nature of the covering of the skin in Birds offers a great 

 obstacle to the reception of external impressions. The toes have but few 

 nerves, and are usually so covered on their under surface, as scarcely to be 

 regarded as tactile organs ; whilst the extremities of the anterior limbs or 

 wings are utterly unsuited to such a function. The sense of touch in birds 

 must, therefore, be chiefly resident in the bill ; this, though usually hard, is 

 soft in the snipes and woodcocks, which search for their food in marshy 

 ground, and also in the flat-billed water birds ; in these it is abundantly sup- 

 plied with nerves. In a few birds the tongue is papillated, and probably 

 serves as a tactile organ. 



Amongst Reptiles the sense of touch is but feebly 'developed. The tongue 

 of the Ophidia, and of many Saurian reptiles, is considered to be an organ of 

 touch. 



The naked, soft skin of the Amphibia is abundantly supplied with nerves, 

 and is, therefore, well adapted for the reception of sensory impressions ; but 

 the proper tactile sense resides principally in the skin over the tip of the jaws, 

 and also in that of the limbs. 



In Fishes the soft lips, the parts about the mouth, and, in some species, the 

 pectoral fins, are the seats of the sense of touch. In a few, as in the gurnards, 

 there are digitate appendages connected with the pectoral fins, which seem to 

 be endowed with tactile sensibility. 



In the Mollusca, touch must be supposed to reside in the general soft in- 

 tegument ; but it seems to be more acute near the orifice of the mouth in the 

 Cephalopods and Gasteropods, and at the margins of the mantle of the 

 Lamellibranchiata. Many are provided with retractile feelers or other appen- 

 dages, specially connected with the head ; such as the horns of the snails, and 

 the arms of the cuttle-fish. The tentacles of the Polyzoa and other Mollus- 

 coida are highly sensitive. 



In the Annulosa, highly developed tactile organs exist, as, e. (/., the jointed 

 antennae possessed by insects, which present the most remarakable varieties 

 of form, and, in certain cases, are so important, that when they are removed 

 these creatures are no longer able to follow their usual habits. In the ants, 

 the antennae seem to be employed as means of communication between differ- 

 ent individuals. In certain cases the palpi and feet may assist the tactile 

 sense in insects. In the Crustacea, generally, the antennae, of which there 

 are frequently two pairs, are undoubtedly sensitive tactile organs, and the 

 prehensile jaws and feet may also conduct tactile impressions. The Myria- 

 pods also have articulated feelers. The Arachnida, which have no antennae, 

 possess palpi ; but the exquisite sense of touch which the spinning Spiders 

 must possess, resides probably in the feet, especially in the terminal joints. 

 The ovipositors of many insects probably possess a tactile sense, to inform 

 these animals as to the fitness of the place of deposit for the eggs. In the 

 Worms, there are frequently found appendages in the form of folds, threads, 

 or setae, often arranged in rows on the body, frequently in whirls, or they are 

 confined to the head, a region which, even if destitute of appendages, is 



