THE STRUGGLE FOR LIFE. 217 
formation of the coagulum, or clot, entangles the red disks 
and white cells in its meshes, it then contracts, and grad- 
ually squeezes the serum out of the clot, the latter is then 
seen to be a pale yellow fluid. I have already said that 
the blood subserves two offices, viz: to promote nutriment, 
and carry away waste. The plasma then, fibrine and 
serum together, contain both the nutriment and the refuse. 
The refuse produced by the waste is removed from the 
blood, partly by oxidation in the lungs, and partly by the 
agency of certain secreting glands; these extract the noxi- 
ous elements, and the secretions thus formed are conveyed 
away out of the body. 
The plasma contains, in addition to the refuse, not only 
the fresh nutriment elaborated from the food taken into the 
stomach, but also, various secretions produced by glands 
like the Thyroid, which are not provided with ducts to 
carry away their secretions. I cannot resist the tempta- 
tion, to add to the mention of the thyroid gland, a few 
words concerning one of the most brilliant achievements of 
Medicine during the last few years, especially as it is 
strictly germane to this part of my subject. Enlargement 
of the thyroid, Derbyshire, or Newhall neck, as it was 
formerly called in this neighbourhood, is the cause not only 
of great deformity, but also sometimes of danger to life, 
while absence or deficiency of this gland is the cause of a 
much more distressing condition, called Cretinism: this 
latter disease takes away from the sufferer almost all power 
either of physical or mental exertion. It has now been 
proved, that daily feeding the patient with portions of the 
thyroids of animals, introduces the necessary secretion into 
the blood, and remedies nearly, if not completely, the effects 
produced by the loss of that organ in the patient. To 
complete, as far as is necessary for my purpose, the account 
of the uses of the blood plasma, I have only to add that 
it furnishes the materials, from which the glands secrete 
