Some Tendencies in Anatomical Studies. Cell-Lineage.--While experimental work occupies the center of the stage, at the same time great improvements in morphological studies are evident. It will be only possible, however, to indicate in a general way the direction in which investigations are moving. We note, first, as in a previous paragraph, that the improvement in morphology is generic as well as specific. Anatomical analysis is being carried to its limits in a number of directions. The investigations that are connected with the study of cells afford a conspicuous illustration of this fact. Studies in cell-lineage have led to an exact determination of cell-succession in the development of certain animals, and such studies are still in progress. Great progress also has been made in the study of physical structure of living matter. The tracing of cell-lineage is a feat of remarkably accurate and patient work. But, however much this may command our admiration, it has been surpassed (as related in Chapter XI) by investigations regarding the organization of the egg and the analysis of chromosomes. Boveri, Conklin, Wilson, and others have shown that there are recognizable areas within the protoplasm of the egg that have a definite historical relationship to certain structures in process of development. This is the basis upon which rests the doctrine of pre-localization of tissue-forming substances within the protoplasm of the egg. Anatomy of the Nervous System.--In another direction the progress of anatomical studies is very evident, that is, investigations of the nervous system and the sense-organs. The wonderfully complicated relations of nerve elements have been worked out by Ramon y Cajal. The studies of Hodge and others upon optical changes occurring within the cells of the nervous system owing to their functional activity have opened a great field for investigation. The studies of Strong, Herrick, and others upon the distribution of nerve-components in the nerves of the head and the investigations of Harrison on the growth and the regeneration of nerve-fibers give illustrations of current tendencies in biological investigation. The analysis of the central nervous system into segmental divisions on the basis of functional activity (Johnston) is still another illustration. The Application of Biological Facts to the Benefit of Mankind.--The practical application of biology to the benefit of mankind is a striking feature of present-day tendencies. The activity set on foot by the researches of Pasteur, Koch, and others has created a department of technical biology of the greatest importance to the human race.