574 



REPORT 1882. 



FRIDA Y, A UG UST 25. 



The following Report and Papers were read : — 



1. Report 071 the Influence of Bodily Exercise on the Elimination of Nittog-n. 



See Reports, p. 269. 



2. On. the Early Develnpment of certain Bodenfs. By Dr. Alex. Fraser. 



The author announced, as a preliminary communication, his having ascertained 

 the fact of the e.x:istence in the rat and mouse of an inversion of the layers of the 

 blastoderm, the same as in the guinea-pig. He also descrilied some of his observa- 

 tions, and exhibited microscopic specimens illustrating them. 



3. On the Homologies of the Long Flexor Muscles of the Feet of Mammalia} 



By G. E.DoBsox, M.A., M.B. 



The muscles, with the homologies of which this paper deals, are as follows : — 



1. Fl-jxor diyitorum Jibtdaris = Flcror hallucis lonr/iis (Human Anat.). 



2. FJp.ior diyitorum tibialis = Flexor diyitorum hmyus (do.). 



3. Tibialis jiosficus. 



The various modifications of tlie.se muscles in many .species of the different orders 

 of mammalia were described, the leading ones being illustrated by enlarged drawings 

 of the dissected limbs. E.xaminatiim of a large series of specimens showed that the 

 three mu.scles are represented by their homologues in most mammals, the Jle.ror 

 fihilaris existing in all, and exhibiting but few modifications, while the other two 

 are subject to much variability, and in some instances are severally or collectively 

 absent. Of these the flcrar tibialis was found to Tary very considerably within 

 certain limits, a variability hitherto not understood by anatomists, and attempted 

 to be explained by supposhig the muscle to have undergone fusion witlithe_/?p.iw 

 Jibularisj while, to its real homologue, the names tibialis posticus accessorius, 

 secundus, or internus had been given. 



The author showed that the tendon of the flexor tibialis which, in most species 

 of placental mammals unites in the foot with that of the flexor Jibularis, in many 

 species (belonging to certain families) of insectivora, edentata, and rodentia, and 

 apparently also in all implacental mammals, beeomes .separated from its connection 

 with that muscle, and attaches itself in.stead to some part of the tibial margin of tlie 

 foot, or to the plantar fascia and integument of the sole. An analysis of these two 

 leading conditions of the muscle is shown in the table below, and gives interesting 

 results, the significance of which was fully discussed. 



Flexor iligitorum tilii.ilis. unitcft in tlie foot 

 witli tlie Flexor digitorum flbularis 



/Chrysnclilorida; 

 CenVetidie 



I. ISSECTIVORA 

 TI. ClIIROI'TERA. 



III. Rodentia . 



IV. Edentata . 



V. HlTRAf OlDEA 



VI. Ungulata 

 VII. Proboscidea 

 VIII. Carnivora. 

 IX. Primates. 



Solenodontidai 

 Potamugalidaj 

 Tup.iiid.'c 

 Galeopithecida; 



( Hystricomorpli.i 

 1 Lagomorpha 



Orj-cteropodidEB 



No tibialis posti- 

 cus 



Flexor digitorum tibiali.^. not connected in the foot -n-ith the 

 Flexor digitorum fibularis 



f Talpidre 

 I. IssF.CTivoa.v- Siiricid:c 



I Erhiaceida; 



III. Rodentia 



IV. Edentata 



f Sciuromorpba 

 t Myomorpha 



Dasypndida! 



BradypodidM 



Manidse 



I. Monotrem.vta. 



II. Mausui'ialia. 



> Subsequently published in extenso in the Jourii. of Anatomy and Physiology, 

 vol. s\'ii. (1882-3). 



I 



