Another kind of differentiation in such a cell-mass as we are dealing with is the setting apart of particular groups of cells for various metabolic purposes.
Some species of animals are much more susceptible to the action of certain drugs than others, a condition which depends on obvious or unknown structural or metabolic differences.
The most common diseases of malassimilation (or "metabolic" diseases) are gout, rheumatism and diabetes.
Their metabolic products may induce blood-poisoning or other toxic effects (facultative parasites) though they are not true parasites.
1 Thus they are pro vided with a nucleus which is the centre of cell activity; Pathological both of the reproductive and chemical (metabolic) pro- GelIs.
Loeb found experimentally that increase of metabolic products in muscle greatly raised its osmotic pressure, and so it would absorb water from a relatively concentrated sodium chloride solution.
For the special pathological details of various diseases, see the separate articles on Parasitic Diseases; Neuro-Pathology; Digestive Organs; Respiratory System; Blood: Circulation; Metabolic Diseases; Fever; Bladder; Kidneys; Skin Diseases; EYE Diseases; Heart Disease; EAR, &c.; and the articles on different diseases and ailments under the headings of their common names.
It was also shown that exposure to light, dilution or exhaustion of the food-media, the presence of traces of poisons or metabolic products check growth or even bring it to a standstill; and the death or injury of any single cell in the filamentous series shows its effect on the curve by lengthening the doubling period, because its potential progeny have been put out of play.
The amount of urea, creatin, creatinin, sulphates and phosphates in the urine is diminished, clearly showing that quinine exerts an inhibitory influence over the metabolic processes of the body.
This serves a double purpose, bringing up from the soil continually a supply of the soluble mineral matters necessary for their metabolic processes, \vhich only enter the plant in solutions of extreme dilution, and at the same time keeping the plant cool by the process of evaporation.
It is probable that most, if not all, the metabolic changes which take place in a cell, such as the transformation of starch, proteids, sugar, cellulose; and the decomposition -of numerous other organic substances which would otherwise require a high temperature or powerful reagents is also due to their activity.
The fat-body is therefore the seat of important metabolic processes in the hexapod body.
In the former case the formation of phelloderm is trivial in amount; in the latter, considerable, since this tissue has to replace the cast-off cortex, as a metabolic and particularly a storage tissue.
In the metabolic Hexapoda the resting pupal instar shows externally the wings and other characteristic imaginal organs which have been gradually elaborated beneath the larval cuticle.
The cells in which the fungoid organism is vigorously flourishing are exceedingly active, showing large size, brilliant nuclei, protoplasm and vacuole, all of which give signs of iptense metabolic activity.
It is instructive, further, to trace among metabolic insects an increase in the degree of this dissimilarity.
Bainbridge suggests that a retention of metabolic products may cause the oedema in renal disease, Bradford having previously shown that loss of a certain amount of renal tissue caused retention of metabolic products in the tissues.
The local oedema seen in some nervous affections might be explained on the hypothesis of increased metabolic activity in these areas due to some local nervous stimulation.
The metabolic changes in the cells, however, concern other decompositions side by side with those which involve the building up of protoplasm from the products of which it feeds.
Welch produced oedema of the lungs experimentally by increasing the pressure in the pulmonary vessels by ligature of the aorta and its branches, but this raised the blood pressure only about one-tenth of an atmosphere, while in some of Loeb's experiments the osmotic pressure, due to retained metabolic products, was equal to over thirty atmospheres.