BIBLIOGRAPHY 697 



brane, and the cartilaginous discs at the ends of the bones form the articular 

 cartilages (fig. 324H, J). 



4) Amphiarthrosis. The term amphiarthrosis refers to a condition inter- 

 mediate between synarthrosis and diarthrosis. This condition occurs for ex- 

 ample in the area of the pubic symphysis. 



g. Dermal Bones 



As observed in figure 3 11 A, the primitive mesenchyme of the ghost skele- 

 ton of the embryo underlies the epidermal tube, as well as enmeshing the 

 neural, gut, and coelomic tubes. As mentioned previously, wherever mesen- 

 chyme exists, a potentiality for bony or bone-like structures also exists. Con- 

 sequently, it is not surprising that various types of dermal armor or exoskeletal 

 structures in the form of bone, dermal scales, and bony plates are developed 

 in various vertebrates in the dermal area, as described in Chapter 12. Aside 

 from the examples exhibited in Chapter 12, other important bony contribu- 

 tions to the skeleton of vertebrates may be regarded as essentially dermal 

 in origin. Among these are the membrane bones of the skull (Tables 1, 2, 

 and 3). These bones sink inward and become integrated with the basic chon- 

 drocranial derivatives to form a part of the endoskeleton. Other examples 

 of membrane bones of dermal origin are the gastralia or abdominal ribs 

 of the Tuatera (Sphenodon) and the Crocodilia, the formidable, dermal, bony 

 armor of the Edentata, e.g., the armadillo, and the bony plates on the head, 

 back, and appendages in certain whales (Kingsley, '25, p. 17). All these 

 examples of dermal armor or exoskeletal structures form an essential pro- 

 tective part of the entire hard or bony skeleton of vertebrate animals. 



Bibliography 



Baitsell, G. A. 1921. A study of the de- Hanson, F. B. 1919. The development of 

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Amphibia. Am. J. Anat. 28:447. 17:1. 



Bardeen, C. R. 1910. Chap. XI. The de- . 1920a. The development of the 



velopment of the skeleton and of the shoulder-girdle of Sus scrofa. Anat. Rec. 



connective tissues. Human Embryology. 18:1 



Edited by Keibel and Mall. J. B. Lip- 

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. 1920b. The history of the earliest 



stages in the human clavicle. Anat. Rec. 



Bell. E. T. 1909. II. On the histogenesis 19:309. 



of the adipose tissue of the ox. Am. J. , , ,, r- ^^o^ a . j r cu n 

 ■ Q-412 Jordan, H. E. 1939. A study of fibnllo- 



genesis in connective tissue by the 



De Beer, G. R. 1937. The development method of dissociation with potassium 



of the vertebrate skull. Oxford Univer- hydroxide, with special reference to the 



sity Press, Inc., Clarendon Press, New umbilical cord of pig embryos. Am. J. 



York. Anat. 65:229. 



Goodrich, E. S. 1930. Studies on the struc- Kingsley, J. S. 1925. The Vertebrate Skele- 

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