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and styloglossus muscles representing the outer intercostal type — the 

 hyoglossus as the homotype of the inner intercostals ; the mylohyoid 

 fibres as the representatives of the transversus thoracis posterior, while 

 the transversus thoracis anterior is unrepresented. The anterior rectus 

 series is abundantly clear, as the genio-hyoid, genio-hyo-glossus and the 

 mesial muscle of Bochdalek. Lastly, we have the cranio-facial axis, 

 which presents us with a series of muscles perfectly accordant to the 

 primary type ; an exo-intercostal in the masseter ; an ento-intercostal 

 in the temporal ; a transversus anterior in the buccinator; a transversus 

 posterior in the pterygoids ; and, from the nature of the organs in the 

 mesial line, a completely suppressed anterior rectus. 



The idea of ascertaining the serial comparisons of muscles is not new. 

 De Blainville and Meckel, in a few points, attempted to determine some 

 of these types, and others have done the same ; but to my knowledge the 

 complete comparison of the muscles, serially, has never been wrought out. 

 In the few instances in which Meckel did indicate these relations, he 

 relied only upon external resemblances. Thus he described the sterno- 

 and cleido-mastoid, respectively, as the representatives of the rectus and 

 pyramidalis abdominis, and the two splenii, capiti et colli as their anti- 

 theses, but assigns no reason but that of resemblance. Henle, like- 

 wise, in the passage quoted above, has done the same ; but in the tables 

 above constructed we can see that an uniform and typical arrangement 

 is probable, though varied by segmentation and transference of attach- 

 ments. 



There are two other classes of muscles existing in the vertebrate 

 animal — one a class of tegumental muscles, the panniculus series exem- 

 plified in man by the occipito-frontalis, the external auricular muscles, 

 the facial superficial muscles, the platysma myoides, the mento-hyoid, 

 Lucas' fibres in the axilla, the post-scapular fibres of Turner (" Journal 

 of Anatomy," Part ii., vol. i., p. 252) ; the supra- acromial and supra- 

 gluteal muscles of the same author — a slip which I have seen cross- 

 ing the perineum from over one gluteus maximus to the other in 

 front of the anus. These have nothing to do with the typical muscle 

 series; and the second class, or visceral series, includes the ento-tympanic 

 muscles, the ento- orbital muscles, the ento-laryngeal, the heart — 

 perhaps the diaphragm (although this latter may be but an internal 

 prolongation of the transversus type). The pericardio-thyroid, the 

 hepatico-diaphragmaticus of Knox, the pubio-peritonealis, and the sterno- 

 pericardialis, which I have seen once in man as a true muscle, and once 

 in a young pig. All these are true visceral appendages, and not skeletal 

 in nature, and so must be removed from the list under our review. 



The main principles of the foregoing remarks may be summed up 

 under the following heads : — 



1. The muscular structure of the vertebrate animal is constructed 

 upon a definite basis, or after a definite type. 



2. This definite type is of a corresponding nature in all the regions 

 of the body, with varying degrees of alterations. These repetitions are 



R. I. A. PBOC. — VOL. X. Z 



