Duration

Duration of various biological processes occurring in the animal kingdom, particularly in the human body, may interest a physician from both theoretical and practical points of view. For a more or less correct determination of duration, knowledge is first needed of the rate of development of the corresponding (phylogenetic, ontogenetic, physiological, biochemical, pathological, etc.) processes occurring in the body, as well as knowledge of the conditions that can influence this rate; since this knowledge, even to the present time, for the most part is not at all precise, and since on the other hand the rate or development of the same process is not predetermined in time and often depends on numerous additional factors, the determination of duration in most cases must be made with considerable caution, often only provisionally, indicating for example the duration with an approximation of several hours, days, weeks, and sometimes even years. The greatest difficulties are encountered in determining the duration of evolutionary-biological processes, questions of phylogenetic development, where the dependence of duration on endogenous processes, for example the mutation factor, is most closely intertwined with the action of exogenous factors. In turn, the duration of action of these factors, their relevance, is even more difficult to determine. In questions of ontogenetic development, the determination of duration is made with greater accuracy, for example in questions concerning organogenesis and in general morphogenesis, although even here some deviations are possible, for example phenomena of tachigenesis, accelerated or premature development, senilism—phenomena observed also in postembryonic life (see Hirsutismus). It is sufficient to point out that obstetrics and embryology to this day are unable to accurately determine the duration of pregnancy, fetal development, giving only average and extreme values, which are used in practical life; thus, the terms of normal pregnancy can vary for example from 240 to 320 days, the appearance of ossification nuclei, processes of myelination in the nervous system, maturation and involution of the ovaries, thyroid gland, etc.—all these phenomena at any given moment have only a certain average value of their duration. In clinic and pathology, the determination of the duration of a process often has very great importance. Thus, approximate determinations of the duration of inflammatory processes are possible according to the nature of pus, determinations of the duration of a thrombus according to the degree of its organization, duration of hemorrhage according to changes in blood pigment and tissue reaction, duration of endocarditis according to the degree of sclerosis and contraction of the valves, duration of pneumonia according to the nature of the pleural covering, duration of the period of a disease according to its symptomatology, status praesens of the patient, etc. Great and most often insurmountable difficulties are connected with the determination of the duration of tumors, since neither size, nor spread, nor the very nature of the tumor give substantial data in this respect, the rate of development of both primary tumors and metastases varies greatly; for example, cases have been described of the development of nodes of metastatic cancer of the mammary gland 10-15 years after removal of the main mass of the tumor. All other conditions being equal, the rate of development of pathological processes in children is somewhat higher than in adults, and in the latter higher than in elderly subjects; often in children's pneumonias already on the 3rd-5th day of the disease, abundance of bronchiectases and even development of granulation tissue, phenomena of carnification are observed. The duration of inflammatory and regenerative processes can also vary depending on nutritional conditions; it is well known for example the prolonged course of wounds in varicose veins of the extremities, typhoid, dysentery ulcers—in emaciated subjects. Fluctuations in the duration of inflammatory processes under the same external influences are often connected with the phenomenon of allergy, hyperergy (see).-Particularly important is the determination of duration in various cases of forensic medical examination, for example determination of the time of death, duration of finding a corpse in water (maceration), in the ground (putrefaction), duration of the existence of various wounds, blood, semen stains, etc. (see Material evidence, Corpse, Maceration, Wounds). In these cases, all the above regarding fluctuations in the terms of duration, regarding the value of numerous external factors affecting the condition of the objects of investigation (temperature, humidity, nature of infection, etc.), should be weighed with particular care to avoid incorrect or excessively categorical conclusions that could have serious consequences in individual and socio-legal relations.