io6 



BIOLOGICAL PHYSICS 



consequent flexibility of the recto-anal and peri-anal tex- 

 tures, while acting as excretory organisms. The first of 

 these structures is the "filum terminak" (Figs. 37, 38), a 

 structure which is usually regarded as merely ligamentous., 

 but which, to us, represents the continuation of the thecal 

 investments of the spinal cord, and which, if not hollow, is 



FIG. 37. PLAN OF THE SKULL, ETC., OF THE EMBRYO PIG, SEEN FROM 

 BELOW. Magnified ten diameters. (From Parker.) 



tr, cartilage of the trabeculae ; ctr, cornua trabecularum ; fin, prenasal cartilage ; 

 ppg, pterygo-palatine cartilage ; inn, the mandibular arch with Meckel's cartilage ; 

 au, the auditory vesicle ; hy, the cerato-hyoid arch ; thh, the thyro-hyoid ; py, 

 the pituitary fossa ; ch, the notochord in the cranial basis, surrounded by the 

 parachordals (iv) ', vn, facial nerve ; ix, glosso-pharyngeal ; x, pneumogastric ; 

 xn, hypoglossal nerve. 



porous, and therefore still able by capillary circulation and 

 gravitation, to transmit fluid sufficient to accomplish the 

 objects hinted at above ; this structure, we think, will 

 find its natural termination in the coccygeal gland or 

 glomerulus, which will receive its contents and functionate 

 accordingly, but not as a mere ligamentous attachment to 

 the coccyx as ordinarily taught ; or, in other words, the 

 filum terminale will " excrete " or distil its contents into 

 the coccygeal gland or into what seems to be a ductless 



