SHEEP DISEASES: THEIR CAUSES, NATURE, ETC. 169 



The blood is not a formed, it is a. formative tissue ; it is not 

 a simjsle fluid, but a highly complex one, and, like all complex 

 matter, is very susceptible to the action of surrounding influ- 

 ences. It is made up of fluids and solids which bear a definite 

 proportion to each other, and any departure, past moderate limits, 

 from this correlation inevitably produces grave consequences. 



I do not vvdsh you to imagine that the blood is every day and 

 every hour the same ; the opposite is the fact. Probably it is 

 never the same for even consecutive minutes of time. Now its 

 fluid elements are in excess, then its solids. One hour it con- 

 tains more saline elements than are absolutely necessary to 

 enable it to perform its function ; another it is deficient in such 

 elements. One minute its flesh-forming constituents predomi- 

 nate, the next its respiratory ; but all the while a certain and 

 necessary correlation is kept up. Cross the boundary line, and 

 health ceases to be maintained, nutrition becomes impaired, the 

 vital elements of the cell elements of the body gain not their 

 normal stimuli and support, and disease takes the place of health. 



I have said that the blood is composed of fluids and solids. It 

 will, perhaps, astonish a few when I say that the proportion of 

 water in 1000 parts of blood is between 800 and 900, but this 

 water, large as the quantity appears to the uninitiated, is abso- 

 lutely necessary to preserve its normal fluidity and to enable it 

 to circulate freely through the great streams and little rivulets 

 of the system. As well might the farmer attempt to irrigate 

 his pastures with mud, as the heart and arteries to circulate the 

 blood if its volume of water were materially diminished. 



Not only is this water necessary for the purpose of facilitating 

 the distribution of the blood, it performs the office of preserving 

 the solubility of the materials necessary for the support of the 

 system — of preserving, in other words, these materials in the con- 

 dition in which they may be absorbed and assimilated ; and in 

 order to render this solution perfect it contains certain chemical 

 substances of an alkaline nature which possess the property in 

 themselves of dissolving, or, more accurately speaking, of hold- 

 ing in solution the albuminous and fibrinous substances (colloids) 

 of which the flesh (muscle) is composed. Amongst the other 

 chemical constituentsof theblood we have soluble phosphatic salts, 

 i.e., phosphate of lime and magnesia, both absolutely necessary 

 for the building up and nourishing of the bony frame and the 

 nerve and brain tissues. Carbonaceous material, fats (hydro- 

 carbons), and starch, sugar, &c., are also important elements of 

 the blood serum, as by them the fatty tissues are supported, and 

 food for resj)iration and the production of heat by oxidation is 

 supplied. 



The so-called solids of the blood consist of little bodies, known 

 as cells or corpuscles ; and inasmuch as some of these are colour- 



