780 SENSE ORGANS AND INTEGUMENT OF THE DOG 



border forms a pouch below its middle, and is thick and rounded in its basal part. 

 Here the conchal cartilage bears a pointed process (Processus uncinatus), which pro- 

 jects upward and backward. The outer wall of the cavum conchse is supported 

 by a cjuadrilateral plate (Tragus) above and a semiannular cartilage below. The 

 concave surface presents several cutaneous folds, and in the cavum conchse there 

 are ridges and irregular prominences. There are long hairs on the borders, apex, 

 and the folds of the concave surface, but the skin of the cavum conchse is bare. 

 The annular cartilage is a complete ring. The osseous external auditory meatus 

 is wide and extremely short. 



The auricular muscles are thin. The scutularis is extensive and is divisible 

 into interscutularis and fronto-scutularis. It partly covers the occipitalis muscle, 

 which is oval and unpaired and ends in the fascia of the frontal region. The 

 scutulo-auriculares superficiales, inferior et accessorius, and the cervico-scutularis 

 are not differentiated as separate muscles. The cervico-auricularis superficialis 

 and the parieto-auricularis both bifurcate and are inserted into the base of the 

 concha and the scutiform cartilage. The parotido-auricularis is narrow and almost 

 long enough to meet the opposite muscle. The tragicus consists of two parts; of 

 these the lateral one is long and arises from the border of the mandible above the 

 angular process. The helicis and the verticalis auriculae are well developed. 



The tympanic cavity is very roomy, extending ventrally into the large but 

 simple cavity of the bulla ossea. The tympanic membrane is extensive and oval. 

 The promontory is very pronounced. The auditory ossicles are large. The 

 Eustachian tube is short, and has a fibrous outer wall. Its pharyngeal opening is 

 an oblique slit situated on the lateral wall of the naso-pharyngeal meatus, and is 

 margined internally by a thick mucous fold. 



The cochlea has three and a half turns and is more sharply pointed than in the 

 ungulates. 



THE SKIN AND APPENDAGES 



The skin varies greatly in thickness in different breeds. It is remarkably 

 loose on the dorsal aspect of the neck and trunk, where it can be raised in extensive 

 folds. The coat is also subject to extreme variation in length, thickness, color, etc. 

 The hairs are arranged in groups of three to a large extent. The sebaceous glands 

 are best developed in the short and rough haired breeds. They are largest and 

 most numerous at the li]is, anus, dorsal surface of the trunk, and sternal region. 

 The sweat glands are relatively better developed in the long and fine haired breeds. 

 The largest are found in the digital pads. Coil glands occur in the skin of the 

 muzzle, the perineum, and the paranal pouches. 



On the flexion surface of the carpus and digit there are hairless, cushion-like 

 pads. The carpal pad (Torus carpalis) is situated medial and distal to the accessory 

 carpal l^one. The metacarpal and metatarsal pads (Torus metacarpalis, meta- 

 tarsalis) are the largest and are situated behind the distal ends of the metacarpal 

 or metatarsal bones and the greater part of the first phalanges. They are somewhat 

 heart-shaped Avith two unecjual lateral lobes, and the apex distal. The metapodio- 

 phalangeal joints rest on them when the paw supports the weight. The digital 

 pads (Tori digitales) are oval and are much smaller; they similarly support the 

 second digital joints. That of the first digit is small on the fore limb, and usually 

 absent from the hind limb. Each receives two suspensory bands from the tubercles 

 at the distal end of the corresponding second i)halanx. The pads have a basis of 

 fibro-elastic tissue and fat, which is intimately adherent to the skin and is connected 

 by trabecule with the bones and tendons. The epidermis is thick and largely 

 keratinized, and is studded with numerous rounded papilla which are readily seen 

 with the naked eye. The corium has large papilla, and contains sweat glands and 

 lamellar corpuscles. 



