46 



tendency to curl up at the end. The fibres in the human subject 

 vary in diameter from the one-five-thousandth to one-ten-thousandth 

 of an inch. The acetic acid of ordinary strength does not act on the 

 yellow fibrous tissue, nor after maceration in water or spirit for a 

 very long time does its elasticity diminish. Very long boiling is 

 said to extract from it a minute quantity of a substance allied to ge- 

 latine, but no nuclei or trace of cells can be seen in it when acetic 

 acid is added ; these, however, are very readily shown when the white 

 fibrous element is treated with this acid. 



The yellow tissue is best seen in the Ugamentum nucha of quadru- 

 peds ; it also occurs in the ligamenta subflava of the spine, in the 

 larynx, in the trachea, and in the transversalis fascia, and various 

 other parts of the body ; the finest example of this tissue is to be 

 found in the neck of the giraffe. In November, 1846, I removed 

 from the neck of a large giraffe which had died in the gardens of the 

 Zoological Society, in the Regent's Park, the entire Ugamentum 

 nucha ; when in situ it was six feet two inches in length ; on sepa- 

 rating it from its several attachments to the spinous processes of the 

 vertebra?, it immediately contracted to four feet ; its weight was up- 

 wards of eight pounds ; in its centre it was three inches in diameter, 

 and consisted of an elongated cylindrical portion which received con- 

 siderable addition to its under surface from the spinous processes of 

 the four lower cervical vertebra? ; these portions of the ligament 

 were much flattened, and about one inch in thickness. With the ex- 

 ception of a strong sheath of areolar tissue which passed into its 

 interior, and separated some of the bundles of fibres, the entire liga- 

 ment was composed of yellow elastic tissue. * 



When a portion from the outer surface of the ligament was exa- 

 mined with a power of two hundred diameters, it was found that 

 each fibre presented the usual curled extremities so characteristic of 

 this form of tissue ; but what was most remarkable, the individual 

 fibres" exhibited a series of transverse markings or stria?, somewhat 

 resembling those of Jibrillce of voluntary muscle in particular ani- 

 mals. The transverse markings occur at nearly regular distances, 

 and appear to be produced by the puckering up of an internal mem- 

 brane, whereby minute cells or spaces are formed like those occurring 

 in the hairs of some of the smaller Mammalia. A few of the fibres 

 are represented in Plate X. fig. 3, as seen under a power of fifty dia- 

 meters, and portions of others magnified five hundred diameters, are 

 shown in fig. 4 ; in both these the peculiar striated condition is well 

 exhibited. The diameter of the largest fibres is about the one-five- 



