th ." ▁And ▁yet ▁there ▁is ▁no ▁empir ical ▁evidence ▁in ▁support ▁of ▁such ▁a ▁parallel , ▁Im iel i ński ▁says . ▁S ens ations ▁of ▁hung er ▁and ▁th irst ▁occur ▁due ▁to ▁certain ▁states ▁of ▁phys i ological ▁ins u ffic iency . ▁The ▁feeling ▁of ▁hung er ▁results ▁from ▁the ▁lack ▁of ▁gl uc ose , ▁f ats ▁and ▁am ino ▁ac ids ▁in ▁blood . ▁The ▁feeling ▁of ▁th irst ▁occurs ▁in ▁response ▁to ▁reduction ▁of ▁the ▁water ▁content ▁of ▁t issues . ▁None ▁of ▁similar ▁states ▁of ▁phys i ological ▁def ic iency ▁responsible ▁for ▁the ▁period ical ▁appearance ▁of ▁sexual ▁ar ous al ▁has ▁been ▁revealed ▁in ▁human ▁sexual ity . ▁ ▁M ales ▁ ▁The ▁most ▁obvious ▁response ▁involved ▁with ▁sexual ▁behaviour ▁in ▁males ▁is ▁pen ile ▁ere ction . ▁The ▁use ▁of ▁the ▁volume ▁( or ▁circum ference ) ▁change ▁during ▁pen ile ▁ere ction ▁as ▁a ▁convenient ▁measure ▁of ▁sexual ▁ar ous al ▁was ▁first ▁developed ▁by ▁Kurt ▁Freund . ▁This ▁measurement ▁of ▁blood ▁flow ▁to ▁the ▁male ▁gen it als ▁is ▁known ▁as ▁pen ile ▁ple th ys m ography . ▁This ▁is ▁commonly ▁measured ▁using ▁a ▁stra in ▁gauge , ▁a ▁simple ▁mer cur y ▁stra in ▁gauge ▁en comp ass ed ▁in ▁a ▁ring ▁of ▁rub ber . ▁The ▁ring ▁surr ounds ▁the ▁pen is , ▁but ▁does ▁not ▁con str ict ▁or ▁cause ▁dis com fort . ▁The ▁measure ▁has ▁been ▁found ▁by ▁some ▁to ▁be ▁a ▁reliable ▁and