Abstract
The heart cartilage and chondroid tissues were examined histologically on transverse continuous sections. The specimen used were 20 Japanese toads, Bufo vulgaris formosus Boulenger.
The author is of the opinion that the heart cartilages may be divided into three groups: hyaline cartilage (in 4 caces), chondroid tissue (in 6 cases) and tissue similar to mucous connective tissue (in 10 cases). Of these the hyaline cartilage was found only in the heart of large toads, more than 14cm in body length.
The heaut cartilage was often detected in the proximate portion of the Septum aorticocarotideum dextrum which is a continuance of the Septum medianum. It was found in a portion between 0.10mm and 1.02mm below the branch of the Trunctus arteriosus. Another heart cartilage was discoverd between the connective part of the Septum principalis and the Septum bulbi. Hyaline cartilage found in the heart was always oval in form, and variable in size.
Cardial chondroid tissue was detected in all specimens. At a glance, the structure of this tissue resembled that of elastic cartilage because elastic fibers were contained in the intercellular substance. This chondroid tissue was found in the Truncus arteriosus in a range of 1-2mm from the branching part and was detected in the Truncus impar, but it could not be found in the Bulbus cordis.
Typical chondroid tissue was found in hearts of large toads (14.0-16.5cm in body length) and it had no connection with other heart cartilages.
