Nisus

(ni'-sus). The periodic desire for procreation manifested in the spring season by certain species of animals. Also, the contraction of the diaphragm and abdominal muscles, NITRO for the expulsion of the feces or the urine. N. -formations, Blumenbach's, the force of an aggregate organism which constrains the newly-integrated atoms to take a definite form; the "spiritus rector. ' ' According to Weismann, this is located in an " acce ory idioplasm," consisting of the determinants of the parts to be regenerated.