The error entrenched
Hidvegi and Hesseltine (1966) proudly celebrated
use of the Hesseltine clamp for nearly three decades:

    "In May, 1937, a report was given of a simple
    and safe umbilical cord clamp.  Directions were
    advanced for its use and documentations of it
    reliability and safety were stated...
    ...It has been used routinely at this institution on
    some 90,000 newborns since July 1, 1937.
    ...Improvement has been made recently by the
    placement of serrations on the proximating
    surfaces of both arms.. These imprints provide
    added resistance to slippage if the cord is
    unintentionally severed adjacent to the clamp.
    ...The device as designed will withstand
    pressure up to 200 mm mercury." [1, p567]

    "The manufacturer (The American Coil Spring
    Company) reports the six millionth (6,000,000)
    clamp was produced on July 15 1965...  
    Obviously, then, a minimum of six million babies
    have been treated by the clamp... each clamp
    has been used an average of five times at a
    minimum.  On this assumption, six million clamps
    represent a usage upon, at least, 30 million
    newborn infants.
    ...This one unit instrument is uncomplicated in
    application, reusable inumerable times and
    economical in service... Another advantage is
    that if the instrument is unsatisfactorily located,
    it can be easily removed and confidently re-
    applied." [1, p568]

The American Coil Spring Company of Muskegon MI
remains a thriving business, though umbilical clamps
are not advertised on their website:
http://www.americancoil.com/

Hesseltine (1937) introduced this clamp with the
following remarks:

    "Many types of instruments and appliances
    have been devised and used to replace ligation
    in the care of the umbilical cord of the newly
    born infant.  Ligation is still the most commonly
    used but it popularity is obviously waning.  Any
    successful method must provide complete
    asepsis, proper hemostasis, and normal wound
    healing." [2, p884]

Instructions on time of clamping were not given as
they were by Wechsler (1912) or Dicks (1925), who
both stated that the clamp should be applied after
pulsations in the cord had ceased [3, 4].

It seems clear though that by the 1930s collection of
umbilcal cord blood to be stored for transfusions had
become popular.  Therefore, Hesseltine's remarks
about the pressures the clamp should withstand
make it apparent that this and other clamps were
already applied before pulsations in the cord had
ceased:

    "Since Nov. 15, 1935, to the present time over
    1,500 unselected babies have had their cords
    treated by this method.  Since the systolic blood
    pressure of newly born infants probably does
    not exceed 100mm mercury and these clamps
    prevent vascular leaks with pressures in excess
    of 250 mm. mercury and do not slip, there
    should be no bleeding.  This contention is
    verified by complete hemostasis in all
    applications." [2, p885]

Introduction of more clamps
Payton (1960) introduced yet another clamp, a nylon
disposable clamp with a snap to prevent its
reopening once clamped shut:

    "Ideally, the obstetrician and pediatrician have
    several aims in mind when severing and
    occluding an umbilical cord during the third
    stage of labor.  The primary aim is complete
    hemostasis of any sized cord, preferably
    obtained without cutting into the jelly of
    Wharton." [5, p1024]  

Thus permanent clamping during the third stage of
labor was apparently common by the 1960s.

Mayer (1964) described a clamp combined with
scissors, introducing it as follows:

    "It is present obstetric practice at all deliveries,
    whether vaginal (with or without forceps) or
    caesarean section, to clamp the umbilical cord
    in two places and cut between them with a pair
    of scissors.  The clamps usually used are pairs
    of Spencer Wells forceps or the new type
    disposable plastic clamps.

    Such a series of actions is necessarily time
    consuming at the very moment when valuable
    seconds could be spent in infant resuscitation
    or maternal haemostasis." [6, p1692]

Thus what Apgar had referred to as "slow birth,"
waiting for pulsations of the cord to cease, seems to
have been completely forgotten about by the mid
1960s.
References
  1. Hidvegi IG, Hesseltine HC
    (1966) The Hesseltine cord
    clamp.
  2. Hesseletine HC (1937) A
    simple, safe and
    economical cord clamp.
  3. Wechsler  BB (1912)
    Umbilical clamp.
  4. Dicks JF (1925) Treatment of
    the umbilical cord by short
    ligation and the use of a
    clamp.
  5. Payton HW (1960) A nylon
    disposable umbilical cord
    clamp.
  6. Mayer TC. Combined
    umbilical scissors and cord
    clamp.
Full References
  1. Hidvegi IG, Hesseltine HC. The Hesseltine cord clamp. Northwest Med.
    1966 Jul;65(7):567-8.
  2. Hesseletine HC. A simple, safe and economical cord clamp. Am J Obst
    Gynecol. 1937 May; 33:884-5.
  3. Wechsler  BB. Umbilical clamp.  Am J Obstet Dis Women Child 1912; 60:85-
    6.
  4. Dicks JF. Treatment of the umbilical cord by short ligation and the use of a
    clamp. Am J Obstet Gynecol 1925 Nov; 10(5):706-8.
  5. Payton HW. A nylon disposable umbilical cord clamp. Am J Obstet Gynecol.
    1960 May;79:1024-5.
  6. Mayer TC. Combined umbilical scissors and cord clamp. Br Med J. 1964
    Jun 27;1(5399):1692. Online at: http://www.pubmedcentral.nih.
    gov/articlerender.fcgi?tool=pubmed&pubmedid=14147753  
top
Combined Umbilical Scissors and Cord Clamp.  From Mayer (1964)
Combined Umbilical Scissors
and Cord Clamp.  
From Mayer (1964)