INTRODUCTION xxxi 



organisms there is an ingoing endosmotic or nutritive current and the outgoing exosmotic or waste product current. 

 These currents vary in activity at intervals. The ingoing and outgoing currents are largely determined by the 

 osmotic nature of the wall bounding the cell, and by the varying densities of the fluids within and without the cell. 

 The mgoing and outgoing currents, essentially osmotic in their nature, occur in individual cells, and are to be 

 regarded as primary, fundamental currents. Given living cells, cell contents, cellular plants and animals, plus 

 moisture, ingoing and outgoing currents become a necessity. These currents are indispensable aUke to the 

 lowest and highest plants and animals. Plants and animals can have no health as apart from the more or less 

 constant inflow and outflow of gases, fluids, and semi-solids into and out of their bodies. The ingoing and outgoing 

 currents are required to change at shorter or longer intervals all the particles entering into the formation of plants 

 and animals, and plants and animals are healthy in proportion as the currents are vigorous, well maintained, and 

 duly balanced. If the ingoing currents are in excess there is turgescence, oedema, and swelling ; if defective, there is 

 shrinkage and diminution of bulk. From the foregoing, it will be evident that plants and animals, and all parts 

 thereof, are constantly changing, and that there is no such thing as stability, in the hteral acceptation of that term, 

 in the organic kingdom. The same is to be said of the inorganic kingdom. The want of stability or the ceaseless 

 ebb and flow of matter without and within living plants and animals make the examination of atoms and molecules 

 imperative in the present work. This follows for four reasons : — 



(a) Plants and animals are primarily and fundamentally composed of atoms and molecules, and these, in turn, 

 form cells and cell structures. 



(6) Atoms and molecules are continually entering into and leaving plants and animals. 



(c) Reproduction and growth and all the changes occurring in plants and animals are dependent on atoms and 

 molecules, and the cells formed by them. 



(d) Movements of all kinds, be they great or small, connected with the circulation, respiration, locomotion, &c., 

 originate in atoms and molecules. 



In the present work I propose to deal more especially with hfe, growth, and movement as indicating design ; 

 life determining the amount and direction of growth ; growth determining form, particularly radiating, concentric, 

 and spiral form, and life, growth, and form determining movement ; notably the centripetal, centrifugal, and spiral 

 movements ; the latter occurring in cHmbing plants, the viscera, the circulation, and in walking, swimming, 

 and flying. 



I also deal, incidentally, with the reproductive and nervous systems ; a knowledge of both being necessary to 

 a just comprehension of the activities of plants and animals. A nervous system, or its equivalent, there is reason 

 to believe, may be predicated of plants and animals ahke. The parts of the work devoted to the viscera, the circu- 

 lation, and the locomotion of animals were largely written by me in the form of Memoirs communicated to, 

 and published by, various learned societies between the years 1864 and 1873. Of these and other contributions I 

 append a list : — 



"On the Arrangement of the Muscular Fibres iu the Ventricles of the \'ertebrate Heart, with Physiological Remarks." (Proc. Roy. Sue. 

 Land., April 19, 1860, and Phil. Trans., Part II., 1864.) 



"On the Relations, Structure, and Functions of the Valves of the Vascular System in Vertebrata." (Trans. Roy. Soc. Edin., vol. xxiii., 1864.) 



" On the Ganglia and Xerves of the Heart and their connection with the Cerebro-spinal and Sympathetic Systems in Mammalia." (Proc. Roy. 

 Soc. £diii., 186.5.) 



"On the Muscular Tunics of the Stomach in Man and other Mammalia." (Proc. Roy. Soc. Lmid., 1867.) 



' ' On the Muscular Arrangements of the Bladder and Prostate, and the Manner in which the Ureters and Urethra are Closed. ' " (Phil. Trans. , 

 Part I., 1867.) 



"On the various Modes of Flight in Relation to Aeronautics." (Proc. Ro^j. Inslit. of Great Biiliiin, March 22, 1867.) 



"On the Mechanical Appliances by which Flight is attained in the Animal Kingdom." (Trans. Linn. Soc, vol. xxvi., read June 6 

 and 20, 1867.) 



"On the Physiology of Wings ; being an Analysis of the Movements by which Flight is Produced iu the Insect, Bird, and Bat." (Trans. Roy. 

 Soc. Edin., vol. xxvi., 1871. Received by the Society, August 2, 1870 ; read January 16. 1871.) 



"On the Relation of Plants and Animals to Inorganic Matter, and on the Interaction of the A'ital and Physical Forces." (Lancet, 

 November 5, 1873.) 



"Animal Locomotion, or Walking, Swimming, and Flying." (Anglo-American Series, London, 1873.) 



"The Physiology of the Circulation in Plants, iu the Lower Animals, and in Man." (Edin. Med. Journ., 1872 : Macmillan k Co., Loud., 1874.) 



" Man in his Anatomical, Physical, and Physiological Aspects." (Lancet, November 1875.) 



"Flight and Flying Macliines." (Ency. Brilannini, 9th ed., vol. ix., Edin., 1879.) 



"The Phonogi-aph or Speech Recorder in its Relation to the Human Voice and Ear." (Modern Thought, February 1882.) 



"Creation — Man's place iu Creation — his Development and Education from a Science Point of View." (Brit. Med. Journ., November 1882 ; 

 and Educational Times, December 1882.) 



" Civilisation a Result of Intellectual Progress." (Not yet published.) 



" The Brain and Nervous System in their Relation to Mind, or the Correlation of the Physical and Psychical Forces." (Not yet published.) 



"On the Formation of Crystals, Dendrites, Spiral and other Structm-es in Relation to Growth and Movemeut, especially Rhythmic 

 Movement." (Edin. Med. Journ., March and April 1901.) 



