858 QUEENSLAND AGRICULTURAL JOURNAL. [1 Ocr., 1899. 
The process of increasing the cells newly formed in this way continues; the 
earliest formed cells are pushed upwards through the column of epidermal ce. h 
that protrudes downwards, and the hair so formed pushes itself finally throug 
the epiderm as a finally developed hair shaft, in which we observe three parts 
DIFFERENTIATION OF HAIR-SHAFT AND SHEATH. 
. Horny layér. 
. Mucous membrane. 
. Central cellular contents. 
. Layer of cylindrical cells of process. 
. Basement membrane, 
. Papilla. 5 . 
. Small light-coloured cone representing the first stage of differenti 
! of the shaft of the hair and its sheath (h). 
Fat globules. 
Origin of the sebaceous gland. 
Qateanace 
‘ation 
S 
. 
Firstly, the outer covering or epiderm; the next portion called the cortical laye"; 
and thirdly, the central channel or medullary substance. 
Beginning at the surface, we find that the covering of the hair—the 
epiderm—is made up of a thin coat of flattened cells which the hair carried a 
with it from the lower and softer portion of the epiderm, or Malpighian muct* 
Having firmly adhered to the hair shaft, having gradually been pushed ee 
through the narrow opening in the skin, and being then expres to the influene 
of atmosphere, this coat of originally slimy or mucous cells became more firm a0" 
tough, thus soe a strong coat that can only be removed through the use ® 
strong chemicals. The microscope shows us the epiderm of the hair shaft asa pres 
regular layer of flattened scales not unlike the tilés on a roof. (Plate OXXXV: 
Before the young hair has penetrated the epiderm and reached the outside 
some of the epidermal cells, situated along the shaft, have reatly increase! 
size and become modified until they have changed into glands, which produce 
fatty substance called the “yolk” of the wool. 
On 
Pete 
ce 
Futty DrveLopep SEBACEOUS GLAND. 
The fat, or yolk, here prepared passes, by means of a duct, to the inner surface 
of the sheath, and serves to cover the young hair with a coat of grease. This; } 
