犬の乳頭式に関する発生学的並びに解剖学的研究

第二報初生犬と成犬について

抄録

According to textbooks of veterinary anatomy and mammalogy, the mammae of dogs are usually 10 or 8, or rarely 11 or 12 in number. However, it is difficult to distinguish the standard type of the mammary formula of the dog from those descriptions. Author studied embryologically and anatomically the mammary formula of the mongrel dog in postnatal stadium, using 49 cases of 9 new-borns and 40 adults, as a sum total. The results obtained are summarized as follows.
The mammary formula was classified into 3 types in new-horns and 9 types in adu lts in number respectively. In adult dogs the moststandard type was 1+2+1 =8 in about a 45% frequency. The mean value of the teat number was 8.888±0.025 in new-born and 8.150±0.037 in adults. The differences among those mean values, including 9.458±0.055 in canine fetuses, are statistically significant. From those results, it was found that there is a continuous change from the manymammae type of the dog in embryological stadium to the few-mammae type of the dog in postnatal stadium.
The degeneration or absence of teats occurred frequently in the anterior pectoral region of adult dogs.