290 SUMMARY OF CURRENT RESEARCHES RELATING TO 



without teeth. This type includes shield-like scales (as in sturgeon, 

 Falseoniscus, and some Plectognaths) ; spine-like scales (as in the 

 lumpsucker) ; and the familiar cycloid and ctenoid scales. The tooth 

 scale is oldest, the placoid next. Gradually the importance of the 

 plate-portion increased and that of the tooth-portion decreased. It is 

 possible to bring the numerous different types of scales into a genetic 

 series. 



Structure of Elastic Intima of Arteries.* — Gr, Carl Huber finds 

 that the stainable substance of this layer consists of a network of yellow 

 -elastic fibres, with the coarser fibres having in the main a course parallel 

 to the long axis of the vessel. These fibres present frequent anastomoses 

 and cross bridges. There are also finer fibrils pervading the network. 

 Here and there certain fibres of the intima may in cross or oblique 

 sections be traced in anastomosis with elastic fibres of the media. The 

 term fenestrated membrane is inappropriate and should be discarded. 



Bone Architecture. t — J. C. Koch has undertaken exact mechanical 

 analysis of the structure, external and internal, of the normal whole 

 femur, with a few to the determination of the relations between structure 

 and function at every point. He believes that the evidence warrants 

 the following conclusions : — The normal external form and internal 

 architecture of the human femur results from an adaptation of form to 

 function. The proportions of the femur are everywhere such as to 

 show a definite mathematical relationship between the body-weight and 

 the internal structure of the bone ; there is a definite relation between 

 the structure and the stresses at every section. Spongy bone is homo- 

 geneous with compact bone as a structural material, and differs from it 

 mechanically only in possessing smaller strength, approximately in 

 proportion to its relative density compared with compact bone. The 

 structure of the femur is based upon the mathematical requirements of 

 mechanics, and the inner architecture is such as to produce great 

 strength with a relatively small amount of material ; the material is 

 arranged to correspond with the stress requirements existing at every 

 section. The adaptation of form to function proved mathematically for 

 the normal human femur is the general law of normal bone. The 

 thickness and closeness of spacing of trabecular in bone varies directly 

 with the intensity of the stresses transmitted by them. 



c. 



General. 



Absorption from Serous Cavities. t: — P. G. Shipley and R. S. 

 'Cunningham have studied the passage of foreign fluids through the 

 walls of blood-vessels and lymphatic vessels. Histological preparations 

 show very active absorption of foreign fluids through the peritoneal 

 blood-vessels. In all probability fluids may be removed from the 

 peritoneal cavity through any area in which blood or lymphatic vessels 



* Anat. Record, xi. (1916) pp. 169-75 (1 fig.). 

 + Anat. Record, ii. (1917) pp. 383-5. 

 X Anat. Record, xi. (1916) pp. 181-90. 



