250 DESIGN IN NATURE 



In the foetal heart they are 120 or so to the minute ; in the adult heart from 60 to 80 to the minute ; in the 

 bladder they recur every four hours or thereby ; in the rectum every twenty-four hours or thereabouts ; in the menses 

 or uterine discharges every month, and in human parturition at the end of nine calendar months. 



I propose to divide rhythms primarily into two great classes, namely. Inorganic and Organic. 



Under Inorganic Rhythms I include : — 



1. Those great cvcles of time during which countries and continents have their climates changed, from 



excessive heat to excessive cold. 



2. The annual revolution of the earth round the sun. 



3. The seasons. 



4. The rotation of the earth on its axis every twenty-four hours. 



5. The alternations of day and night. 



6. The waxing and waning of the moon. 



7. The rise and fall of the tides, &c. 



Under Organic Rhythms I include the changes and movements occurring in plants and animals at stated and 

 calculable intervals. They are connected with and more or less intimately dependent upon the inorganic rhythms 

 referred to above. 



In Plants the chief rhythms are : — ; 



1. Those connected with reproduction and germination. 



2. Those connected with the rise and fall of the sap. 



3. Those connected with the production of the leaves, the flower, and the fruit. 



4. Those connected with the fall of the leaf. 



5. Those connected with the regular movements of different parts of plants, such as occur in leaves and 



branches, the opening and closing of stomata, the opening and closing of vacuoles or water spaces, 

 respiration, circulation, &c. 



6. Those connected with the movements of ciha in spores, &c. 



7. Those connected with the alternate action and inaction of plants as a whole, as influenced by the 



seasons, day and night, nutrition and innutrition, &c. 



8. Those connected with the periodic intake and output of sohds, semi-solids, gases, &c. These have 



a direct bearing on the building up, nutrition, and maintenance of the plant. 

 In Animals the principal rhythms are : — 



1. Those connected with eating and drinking (set meals). 



2. Those connected with the organs of alimentation (oesophagus, stomach, bowels, rectum, bladder, &c.). 



3. Those connected with waking and sleeping. 



4. Those connected with respiration. 



5. Those connected with the circulation. 



6. Those connected with the emotions. 



7. Those connected with reproduction. 



8. Those connected with locomotion. 



Under 1 (Eating and Drinking) fall the rhythms engendered by the desire for food and drink at stated intervals. 

 Under 2 (Organs of Alimentation) fall the rhythms occurring in :— 



(a) The fauces and oesophagus. 



(&) The stomach with its sphincters. 



(c) The small and large intestines. 



{d) The rectum with its sphincters. 



(e) The urinary bladder with its sphincter. 



winkhi'"^!'^ ^^^^'""^ '"""^ ^'''^'''^^' ^""^ *^' '^^*^"'' engendered by alternate activity and repose, hibernation, 



Under 4 (Respiration) fall the rhythms occurring in :— 



(«) The nostrils. 



(6) The glottis. 



(c) The lungs, or parts thereof. 



{d) The diaphragm. 



(e) The muscles of the thorax, abdomen, &c. 

 Under 5 (Circulation) fall the rhythms occurring in :— 



(a) The blood-vessels. 



(6) The several compartments of the heart. 



