Origin and development of the muscles of the intermetacarpal space of the forelimb of Felis catus.

Abstract

This paper demonstrates the structure and development of the layer of mm. flexores breves profundi in Felis catus (Carnivora). By microdissections of the deep palmar musculature, it was found that there were formed two muscle layers: 1) four muscles beginning on the palmar side of the carpus, passing distally through the intermetacarpal spaces and inserting into the dorsal digital aponeurosis of the second to fourth digit--the superficial muscle layer of mm. flexores breves profundi; 2) four muscles beginning on the palmar area of the second to fifth metacarpus and inserting into the capsules of the metacarpophalangeal joints of the second to fifth digit--the deep muscle layer of mm. flexores breves profundi. Ontogenesis of these muscle layers was studied on 35 histological series of embryonal extremities. In early ontogenesis we found a coherent cell condensate of the anlage of mm. flexores breves profundi layer. Differentiation of the anlagen of individual muscles takes place in the foetuses of 17-20 mm crown-rump length. In embryos of 17-19 mm crown-rump length a small cell condensations corresponding to the layer of mm. intermetacarpales anlagen were found in the second and third intermetacarpal spaces. Both anlagen are formed only temporarily whereafter they break into fragments and extinct.